[Sowexly]

My 595s haven't arrived yet but I've owned a pair of Ultrasone 900s (do I miss them so) long story short; I found a nice deal on some used 595s
I've heard I don't need an amp to drive them but I was thinking about getting the Xonar STX to help give them some kick, any other more modern recommendations?

 

[imacguy]

Far from an expert here, but I think my 595s run well with my Fiio E7. I'd consider getting an external DAC/amp instead, though others may differ on that. It does seem like the cheaper alternative though. The E10 is only 75 on Amazon for instance.

 

[Sowexly]

I'm looking to get the Xonar used too for around 130 and I won't need portability with these cans.

 

[ZARIM]

The Essence ST/STX willbe better for these cans and they are easily customizable like rolling OPAMPs. But external AMP/DAC like iBasso D7 are even better sounding because better DAC and dedicated Amlifier.

 

[PurpleAngel]

For $130, the Essence STX is a good buy, good all around sound card for doing any audio on a computer.
The Essence STX (&ST) are best for headphones that are 100-Ohms or higher, HD595 are 50-Ohm.
The Xonar DGX ($46) can do a fairly decent job of driving the HD595.
I'm not claiming the Xonar DGX will do a better or equal job of driving the HD595, but for the price ($46) is save you cash for something else.
The amplifier on the Fiio E10 should be able to match the STX for driving the (50-Ohm) HD595.
The E10 design is better for driving 50-ohm headphones over the STX.
 
In all fairness right now I'm sitting in front of my PC using HD558s, listening to the BeeGees (You should be dancing) with my STX (AD797BR op-amps) and it does sound nice.

 

[proton007]

Essence STX has a dedicated DAC and dedicated amp. 124dB S/N, -110dB THD is better than the iBasso.
I wouldn't say external DACs will be definitely better, unless can be proven with measurements.