"Ideally" would be three Dell UltraSharp U3011, but..
$4200

I realize with resolutions higher than 2560x1024 you start running into walls because cards sometimes don't support resolutions higher than that, but just wanted to mention that I ran LFS at 2560x1024 for quite a while on a 6800GT perfectly fine, so I highly doubt that with newer cards it really is a lack of raw power...

...just a lack of good drivers.

Im currently running 4000x1024 with a 250GTS + secondary card. sli mobo with soft th. The cheapest way to go triple screen.
Just for comparisons sake.

If I can find some more desk space, I'll consider getting another U2711 and get about 5120x1440, It should run fine with 2 470's, b\however I'll have to turn it down on games like GTA4 and Crysis (maybe 2).

Quote from dadge :

aye. ideally, i'd love to get 3x32" tv/monitors. but you're looking at close to £1000 for the 3 of them. projectors are becoming really affordable too. could be worth a look (no bezels to worry about).

Peats had 37" sony LED's for just under 400 quid, i gots me one for the Gf's family but by the time i went back ( litterally within 2 hours ) they where all gone....

and Frankly im not surprised... would be overkill though.