If you're the guy who posted on Reddit earlier today, then well, you know a lot of this already:
Beyer owner here. I've had a set of DT770 Pro-80's for about five years now. You know, the rugged all-black plastic ones. For the past two years, I've worn them every day, 7-ish hours/day while at my desk. They're extremely comfortable and sound awesome driven by my old computer (24" iMac) and my new one (Mac Pro) without any additional amplification. Also, they can be had for under $200 brand-new. The treble IS detailed, some say exaggeratedly so but I can't complain. The bass is extremely deep and tight, pronounced but not boomy in my experience. (For reference, I would use "boomy" to describe Bose QuietComfort, Monster Beats Pro, B&W P5 and the Beyer DT235.) Some people will tell you that the beyer "pro" models all clamp too tightly on your head, but the magic of Beyers is that it's easily adjustable. Unlike Sennheisers with their fat plastic headbands, the Beyers have a sturdy piece of steel comprising the backbone of the headband. This piece of steel has an easily-replaceable cushy pad snapped over it. In order to "adjust" them to your head, you just lightly bend the headband out, try for fit, repeat until they're loose enough that you don't notice them anymore. For more pressure and isolation, bend them back in again. The earcups are really deep so that the speaker grille doesn't press up against your ears (a big problem for me with most headphones) and the velour pad is soft and more than big enough to completely surround your ears.
I briefly listened to the DT990 Premium 32-ohm model last week and thought they sounded friggin' fantastic, but can't say if they'd replace my 770's. The soundstage was noticeably bigger and they were more bassy than the DT880's next door, but I'd need some quality time to determine if they're significantly better than the 770 Pros. Being an open design, though, they suffer a bit for my purposes by leaking sound in both directions. I'd still consider picking up a pair for listening at home, at the right price. I'd be curious as to how they stack up to my Grado SR225's, my dedicated home headphone.
I built an 18v Cmoy almost a year ago and didn't hear any improvement with the 770. Haven't used it since a month after I built the thing. I also later bought a NuForce uDac2 which I returned after a week-- it gave me more volume but no real improvement in sound quality (plus, benchtop testing says it's actually *worse* than many onboard sound cards, if it really counts). So I continue using my Beyers without an additional amp or DAC, and to my ears the sound is still great. After 5 years of pretty heavy use the earpads have flattened out by about 30%, so just today I ordered a replacement set from B&H for under $30 shipped. Oh, and I've used them while playing FPS games and they're friggin' superb for spatial positioning and detail.
**EDIT** Heck, man. Here you go, $167.95 with free shipping! I'd be surprised if anything could touch this kind of quality (and longevity, and comfort) at that price.
Edited by DocBlasto - 1/4/12 at 4:14pm