*Disclaimer: I received this as a free review sample and did not pay for it

I have been testing the Burson Cable+ PRO A2R 3.5mm to RCA cable.

I used it between my iphone and my imac (both standard 3.5mm outputs on these devices) and my schiit magni 2 amp. First I listened using a standard 3.5mm to RCA cable, then I listened using the Burson Cable+ PRO A2R. I used Oppo PM3 headphones.

These are my thoughts.

I listened to a variety of different types of music, streaming lossless files from TIDAL. I tried to listen to as many genres of music as possible to get a feel for the improvement that the cable delivered, if any.

I listened to the following:

Eagles-Hotel California (rock)
ZZ-Top-Legs (rock/pop)
Paul Simon-Baby in the bubble (80s folk pop)
Motley Crue- Girls, girls, girls (80s hair rock)
The Weeknd- Can't feel my face (hip hop)
All that she wants- Ace of Base (90's pop/dance)
Ice Ice Baby (re-recorded)-Vanilla Ice (90's dance/hip hop)
Vivaldi-Four Seasons (entire album) (classical)
Jogging- YELLE (francophone pop)

These are my thoughts. Overall, the Burson cable seemed to somehow deliver what I perceived as a more punchy and powerful sound. I was actually surprised that this sound was coming from my iPhone 6, and my mac. The sound quality from which I have never been impressed by in the past. There seemed to be more clarity and detail, and overall the sound was more precise and warm. It almost sounded like I was using a decent DAC, rather than an iPhone.

The following are my thoughts on the individual songs I listened to, and my feelings about the burson cable+ versus a standard cable for each:

Eagles-Hotel California (rock)
Immediately when the drums kick in at the beginning of the song I noticed a greater sense of power and presence. The entire song was clearer sounding, and it sounded like I was using a higher quality source than I was. Vocals were more rounded, and the overall sound was more analog than with the standard cable, by which I mean that it didn't sound paper thin the way most digital files normally do.

ZZ-Top-Legs (rock/pop)
The looping guitar riff in this song sounded so much more detailed with the burson cable than it did with the standard cable. I have normally found the vocals in this song to sound rather muddy if not using a high quality source, but in this case they seemed more defined. So far, I was impressed with the Cable+.

Paul Simon-Baby in the bubble (80s folk pop)
I was impressed by the increased punch of the organ and powerful drums at the beginning of this song. The rest of the song for some reason I was not able to discern a major difference between the cables I tested. The Burson cable did sound a bit better but the difference was minor and I'm unable to quantify it in words. The intro section definitely sounded better on the cable+ though.

Motley Crue- Girls, girls, girls (80s hair rock)
This is one of my favorite songs. It sounded "louder" to me with the cable+ which is not a good description, I know, but it definitely sounded punchier and "bigger" somehow with the burson. Sort of like listening on an 80s over the shoulder boom box versus listening on a decent entry level HIFI system. The overall sound with the burson cable was larger and more impressive.

The Weeknd- Can't feel my face (hip hop)
Unfortunately I could not discern any sort of difference with this particular track. Perhaps that is due to the fact that it is "loud" as heck to begin with in the way it is recorded. Certainly, the burson didn't sound any worse, but overall I found both cables too similar sounding to tell a difference. Not to my ears, anyways.

All that she wants- Ace of Base (90's pop/dance)
The vocals in this track, which usually sound flaky and recessed with a cheaper source, actually sounded very good. More "forward" than usual. This is an effect I have found with this song when using a good DAC but I was able to accomplish the same difference using the burson cable+ which certainly impressed me. The rest of the track sounded very similar. There was slightly more depth and a bit more of an analog (not too thin sounding) sound with the cable+.

Ice Ice Baby (re-recorded)-Vanilla Ice (90's dance/hip hop)
The re-recorded version of this song has a digital "hi hat" that hits extremely hard. Almost ear-splitting hard, actually. There was definitely a difference with the burson cable in that it sounded less ear splitting. It was certainly still there and certainly just as loud, but it was somehow less harsh, wider, and better rounded sounding than with the cheap cable. A definite improvement and another point for the cable+

Vivaldi-Four Seasons (entire album) (classical)
Being a classical piece, and an analog (old) recording transferred to digital, there really isn't a lot of dynamics or loudness to this album in the way that there is with a lot of modern music, and certainly there was no difference in this department. I did however notice an improved level of detail and I was perceiving sounds in the background with the cable+ that I did not detect with the normal cable.

Jogging- YELLE (francophone pop)
This is an extremely loud song. The recording engineer had everything at 11, for sure. I did not notice a difference with this song, perhaps because it is so loud to begin with and it's just attacking the ears all the way through.

Conclusions:

Overall I feel that, with the sources I used (iphone 6, imac 2017) and the amp I used (Schiit Magni 2) and the headphones (Oppo PM3) there is definite improvement to be had using the cable+ from Burson. I did not pay out of pocket to test this cable so I can't express whether I would have any sort of buyers remorse or not given the relatively high cost of this cable (at least to a broke audiophile like myself) but it definitely improves the sound quality when using mis-matched devices. I kind of wish I had asked for the RCA>RCA version so I could test it with the schiit Magni and modi stack. However as I understand it, this product (cable+) is intended to be used with mis-matched HIFI devices that are from different mfgs and from different product ranges, and it somehow normalizes the signal between the two devices that are interconnected with it.

Did it make a difference? Yes. Was the difference desirable and positive? Yes. Would I recommend it? Yes. The only knock I have for this product is that the "business" section (a bulge in the middle with the electronics inside) requires power via USB (Usb cable and wall wart come in the box) and I feel like, maybe that's one cable too many? But I'm not complaining.

10/10.

I owned a pair of these. My uncle also bought them. They sound ok for the price. For people concerned with actual fidelity and resolution, you'd be much better off with entry level 4 or 5 inch powered studio monitors. Presonus' Eris 4.5 is a 4.5" stereo studio monitor setup that sounds much better than the promedia- especially with a good source like a decent USB DAC, or even a high end soundcard like an Essence STX. Of course, these don't have a sub. So if you're a basshead and all your music is at a terrible 320kbps or lower, stick with the promedias. If you listen to FLAC/ALAC/WAV or CD's and you want better sound, look at a 4.5 or 5" stereo studio monitor setup. I don't recommend the (strangely popular) Audioengine A5 as an alternative as that speaker is very poor for the price.
 
Basically, at any price point, there are better speakers out there than the Promedias for the "broke audiophile". For people without good hearing, or who don't know what good sound is, or who are bassheads, the Promedia will be fine for you. However, if you want truly good sound quality out of your computer in a one-time purchase, consider tripling your budget and getting the KEF X300A which is a stereo setup consisting of two nice bookshelf speakers which each have their own internal DAC and class A/B amplification. Those sound like true entry level HIFI. You won't get that out of any computer speaker. 
 
In the end, as all audiophiles know, computer speakers are crap. Why? Simply because the manufacturers can get away with it. The average user doesn't expect much from their computer in terms of sound quality. Those of us in the know, know that you can hook a $50 000 HIFI up to a computer and get incredible sound if you do it properly. All computer speakers from $20 logitechs all the way up to $500 AudioEngine's are crap. Some are more crap than others, like the Corsair SP2500 which is monumentally terrible... but none are good. The only truly good computer speakers that ever existed were the short-lived Klipsch iFi which used two actual HIFI satellites (RSX3) and a proper entry level HIFI subwoofer for really mind blowing sound. They were about $500 back in 2005-2007. Exceptional. These days though it's all gutter grade.
 
Save up $700 and get the X300As.