yes...2600k, 2x GTX 590's SLI, or 2x HD 6990's CrossfireX!!!! FTW!!!
Aren't Xeon's for workstations/servers? I recommended single gpu's because I consider them to be more stable than dual's, although dual gpu cards are independently more powerful. That board is a god among men. 48gb of ram? What on earth will use 48gb?
Is there a big difference in performance depending on which card is used for physx? I would think a gt450 or gtx460 would be fine for that.