OK...got the headphones today.

First impressions:

1) highs: nice. no complaints.

2) mid-range bass is a little "bloaty"...hard to describe. Keeps the mids from sounding super clear.

3) low-end. Being as how these are my first pair of headphones, I'm not sure what headphones are supposed to be capable of when it comes to bass. That said, the attack/punchiness of the bass is a little lacking. When listening to the Propellerheads' "On Her Majesty's Secret Service" (my go-to track for bass) it's clear and tight, but doesn't have that ass-kicking, bitch slapping bass I LOVE from that song. Again, not sure what headphones are supposed to be capable of in regards to bass though.

4) As much as I'd love them to, they aren't going to recreate the experience of my beloved M60+EP500 combo.

5) they're BIG! If for no other reason, I may have to return them as they're just a tad too big and there's no way to adjust them at all (is that as odd as I think or are most headphones non-adjustable?) I'll be wearing these for up to 8+ hours per day. The ATH-900X's are a wee bit big and tend to slide down over my ears putting pressure on the top of my ears. That starts to get uncomfortable after an hour or so.

Now as far as listening straight off my motherboard...

I found some tracks when pushed a little too hard started to distort badly. Distortion through speakers is bad, through headphones it's borderline painful. Like nails on a chalkboard. Bleck!

Would a supercheap (Creative Audigy SE) soundcard fix the distortion issues?

I'm bummed about the size issue, as I got a crazy good deal on these at Best Buy ($159 vs $299 msrp - gotta love open box stuff!) If I return them, I'm likely going to pick up the Sennheiser HD-598's. Anyone know anything about those? I tried them on and they were super comfortable at the store (and they're adjustable).