I'm pretty much in the same boat as you, but I listen more to electronic music (like kavinsky, justice, daft punk, not much house/deadmau5, never dubstep/skrillex stuff). I listen to a bit of metal/rock though (love some black metal emperor, dimmu borgir, older cof, some heavy like king diamond). Looking for a sub-$200 that's extremely comfortable, 8+ hours usage, don't care for isolation/leakage or portability, something also well rounded as I play SC2 (an RTS) and general media. I use a z87x-ud3h motherboard which has an alc898 + 600 ohm headphone amp DRV632.
There's a guy around here, natsuka, that said the shure 440 is better then the 598s and pretty much everything under $200 (i've used the 240a and they suck and were very uncomfortable, i dont know how close the 440s are to them though as they are supposed to be quite different in sound).
I'm also leaning towards the 558s. I just bought some 681 EVO for my girlfriend, should be similar in comfort to the 668b and sound quality (sound profile is very different though, much more V, colored, bass heavy, not as neutral), curious what you felt of the comfort of the 558s when you tried them at best buy compared to yours 668bs.
I also went to best buy and guitar center, they had some 428s which seemed comfortable enough but couldnt test them on my phone, they were hooked up to some stupid 1-track single so i have no idea how they really sound comparatively as it was an awful song. Best buy has a really limited selection, mostly trendy garbage (holy crap the beats studio suck, piercing highs that have that distortion/muffled sound when you blast sound out of a crappy $1 airplane set you know, overwhelming muffled bass, extremely uncomfortable, pretty much describes everything best buy has for sale though).