6990 is a waste because one core would sit idle just like my 5970. Plus, they come downclocked from 880>830mhz, so the oc would have to be higher. A 7970 would be nice but I hear that the coding for F@H doesn't take advantage of the new GCN architecture and the ppd is on par with a 6870.
*Correction* for Joe
We need someone dedicated to making Dark Predators #1!