First off, why would you want to go to a grey screen? Unless your projector has a horrible BL, I would stick with a white screen, especially seeing as you have a light controlled room.
There are many pj's out there right now that do a great job with blacks, at a reasonable price. I haven't had the opportunity to demo $10,000+ projectors but the one's I have seen have done an excellent job with black level detail (RS1,RS2,1080UB, etc.) Someone correct me if I'm wrong but I don't think there is a projector out there that will do a true black, as none of them are able to completely shut down the light path. They are all projecting a very dark gray.
If you love your Optoma I think you will be pleasantly surprised with the current lineup, and even more so with the new crop on the horizon (RS20, 7500UB).
Psychotic Episode Averted