Having considered all these options ages ago, I went for the DT880 '03 250 ohm before I upgraded to the DT880/600.
The AKG K701/K702 is notorious for being picky amp wise, not to mention the funky fit and unnaturally wide soundstage. Having heard decent $$$ speakers in an acoustically dampened room + HD800's, I know what a decent natural soundstage is and although headphones in general don't offer a 'natural' soundstage, judging apples to apples, the K701/K702's soundstage sounds like you pinched the far left and far right soundstages and stretched them. If you want to see how the K701's soundstage is like shape wise, think of a Bell curve. It isn't a well rounded soundstage. Not to mention they are bass light (despite what all the K701 fanbois and the 'head-fi sound signature' say), particularly when not amped properly. The K701's do have good soundstage depth however. the K701 is very much love it or hate it and as much as I want to like it, I hate it. The SA5000 I've read has gobs of detail but is rather cold sounding. The DT880/600 ohm however I feel is the best within this price range for an all-round headphone. Others feel the same too tbh. It really depends on your music taste though. The K701 is insanely fanboi-ed here. It's not a bad headphone but more the flaws outweigh the positives of it.
Edited by chinesekiwi - 6/28/10 at 9:43pm