Hehehe... got here too Trickmaster! I can't help too much about the dj2000 (used only a few times), other than say it's a daaamn fine mixer but Trickmaster will surelly help u here in a...hmmm... very deep and complete way

I'll play devil's advocate...
The DJM, I own the 600 but spinned a lot using the 500 for it's all over the clubs and gigs here, everyone is pleased w/ it (club owners like it for it gets a lot of puishment and never needs an overhaul). My opinion on the Pio
DJM 500 and 600 is, they are two of the best designed pro mixers ever, everything is so easy to get on it, no one could ever blame it for limiting operation or screwing up a mix for it's all in-your-face as it can be. That's number two for me, something intuitive to use. Even more when u consider the efx that both dj2000 and djm have, even Trickmaster will agree the djm is way easier to operate efx than the dj2000.
Number one is quality. Again, a damn good mixer from top to bottom, high (maybe not the highest but more, much more than enough even for them most demanding dj and sound engineer) quality parts and they didn't skip anything: long lasting faders and knobs, smooth as butta too, good and clear graphics, mic X 2 w/ eq control on main, phono/line switches, it just oozes quality all over.
Feature-wise, it's crammed w/ gadgets as: a considerable (although somewhat limited) number of usable efx, xfader curve selector (only
djm600), split cue (powerfull cueing), multi-cue, cue-master PFL, very usefull individual AND master L/R channel level meters (loong, nice ones not a 4 led fake!), that not to mention the outputs and inputs. Ok, the dj2000 has midi controls, IMO it's nice to have them today...
The 500 looses a few bits & feats to the new 600, like fader curve control (I said that...), efx wet/dry and level control, some efx (not sure which one though) and the split cue, I think it's that. I'd have one or the other, just had a good deal on the 600.
Other than that, it's personal but I like the channel fader curves, the -26/+12 bd eq (well judged bandwidth range) and the sound quality, IMO it's better than Vestax and maybe just a tad bellow the top rigs from Allen&Heath and Rodec (other 2 top contenders mixer-wise), but to a level one could not easily tell the dif. And that's somewhat passionate ground so I'll finish here...
I hope it helps on the djm, it's my opinion but I've used a lot of mixers and I chose the 600 for the reasons and facts above!
Good luck and regars.