I'm with the rest of the people here, Buy the highest resolution/biggest monitor you can buy. 30'' 2560x1600 will be it. If you're not connecting any other input sources into it, i'd recommend Dell 3007wfp-hc.
Oh wow I knew it was a dual GPU card but I was unaware you couldn't take it past crossfire.
Could you imagine four 5970's in quadfire, 8 gpus!
well considering how bad 3 and 4 gpu's scale in crossfire/sli, 8 would be horrendous, in factyou might get to a point of diminishing returns, not to mention for the 5970 to work well it really needs the full pci-e 2.0 x16 bandwidth, so with 4 cards you would need 48 lanes, which no board has (some have the NF200 chip that multiplexes lanes, but it would still be bottlenecked at some point)