Yes the K271 is a little bass light. I A/B'd them with the HFI-580 and the AKG's bass was much milder.
Another time I compared them to Beats Pro and M50--in that instance the K271 felt a little warmer in the mids, and overall more "right" in the treble and bass.
Demo-ing 770 and 550 in store now, unamped and with music.
[Update:] 770 really does have some fantastic bass and soundstage, but I think it comes at the cost of the mids. They feel very recessed. Highs are a bit rolled off too, though that's not necessarily bad. MLE's spot-on: I expect these to be GREAT gaming-for-fun only. Not so great as all-rounders.
K550 looks and feels excellent, but I think I'm hearing the "plasticky" mids AKG is infamous for. Voices sounded a bit unnatural and the highs were a tad peaky. Jazz at the Pawnshop did not sound good at all. Classical violin was perfect. Fit was a bit finicky.
Edited by Eric_C - 8/30/12 at 10:49pm