I don't have a TH-600, but I do own the TH-900, and enjoy it for most of my preferred genres - breaks, deep house, dub-techno, jazzy hip/trip-hop, math-rock, jazz-fusion - more than any other brand's flagship. If the TH600 is anywhere near the 900 in terms of overall sound, then I suspect you'll enjoy it immensely, particularly with music that's bass/sub-bass flavoured.
Amp matching is just as important, particularly if you don't EQ in software. The Fostex TH cans are actually quite easy to drive compared to most of their competitors, but they do have a U-shaped sound signature, so if you pair them with an equally U-shaped sounding amp (or worse, a V shaped one), you might have your mids recessed to the point where they no longer sound natural.
Like ethan700 stated above, the Fostex TH series ranks highly in the comfort department. Something to consider if you listen to multiple hour-long EDM mixes in a row. Personally, the only cans that rival my TH900 in the comfort department are the Senn HD700 and HD800. TH600 should be just as comfy as the 900, maybe even more so, since it's slightly lighter.
Just my opinion, though. It's still best to try em out yourself before making a decision.
Edited by kurochin - 10/24/13 at 10:15pm