I'd say don't even hesitate to get a Rev2, and recommend ponying a few hundred more for the 16 voice, because you're then getting 2 outstanding 8-voice analog polys in a single synth if you chose to run it in split/multi mode, or a synth that probably not much else can compete with if you have the thickness of two sounds stacked.
Don't get me wrong, love my OB-6, but it doesn't have the range/versatility of the Rev2. My next synth may be a P6, or a second OB-6.... but the only reason I say this instead of a second Rev2 is because a single 16-voice Rev2 covers so much territory -- everything else from there out is filling in niche needs.
The other thing is that the Rev 2 has this symbiotic relationship between the hardware and the sounds that I can't describe, like perfect weight to the keys and the impact of aftertouch on the CRAZY amount of modulation possibilities. I've never known an synth that felt more like an instrument to play.
If my Rev2 and OB-6 were compared to people, the Rev2 is more like Peter Gabriel and the OB-6 is more like David Lee Roth