Honestly, I do love my HD25s more than the M50s that I've sold. Although for instrumentals, there isn't as much soundstage which is the only downside I can see honestly, due to the on-ear design rather than over-the-ear. I bought my HD25s for $168 w/.. free? or like $5~10 (don't remember honestly) USD shipping on ebay from a top rated seller (+ authorized). They sound great for both my hip hop and pop / rock / etc. needs
. Bass is crisp, although it doesn't rumble like the M50s, but I had to amp up my M50s to really hear the rumble. Everything sounds better to me on the HD25s despite the fact they have pretty much no sound stage and has basically no rumbling bass (which I do love).
I also have an onboard soundcard, and really, I don't think dedicated audio cards will help THAT much. I've built my desktop from the ground up, and the only thing (well really, two things) that didn't cross my mind was an audio card (and a network card). I don't have experience with 100+ ones, but for say, an E7, I noticed NO difference. Then again it could be just me and my damaged hearing but I kind of doubt so
(but then again my doctors tested me and nothing was wrong with my ears, although I do have tinnitus).
And let me just say that my $25 USD walmart earphones back then (albeit Koss) sounded much better to me than Beats Solo (although I don't know for Studios and Pros, don't recall how they sounded). They were also in-ear monitors though, but they still had better bass to me than Beats. Mids were recessed though, but not as harsh as Beats.
For the open vs closed argument, I honestly don't know because the only open headphone I have had so far were AD700s (and they were for gaming, honestly) and I HATED them. They gave me a headache and I have no clue why (though I hated their pads). I returned them, and the soundstage wasn't much better to me than DT770 Premiums / even the M50s (although the AD700s did have a bit more than the M50s). For soft songs they sounded great though (although I still preferred how my current headphones sound over the AD700s, but I have yet to try others. Thinking about getting some Grados next or something).