I have just recently commissioned a catalyst system with 2 machines consisting of the following:

quad core 2.8
3 120g SSDs
Nvidia Quadrafx 4000
1 tripplehead2go
3 matrox Convertdvi to get genlocked dvi.

Both machines are running 3 1920x1080 displays without a hitch and are synced together. I can get 1 complete set of 1920x1080 with no frame drop and 2 sets of 720p with no frame drop. Plus some additional graphics and Other movies at times.

One thing to note, the quadrafx 4000 will only output dual link with a high enough res on the dvi output only.the display port will only go to 2500 ish pixels wide, not the 3840 needed for 2 x 1920 outputs needed with a triple head. Or you could only get that 4 way box mentioned above to work on that card and probably won't get the second port to work at all.

The single 20k with a super wide lense Is terrible looking. Great for easy and fast setup, but this would highly disappoint your client I would guarantee you.

I would definitely say use at least 2 servers. One can't do all that. And more is better depending on what your layering needs are.