I already have a full HD 24" monitor, but was hoping to increase the feild of vision so the resolution goes to 5440 x 1080i - seen something similiar for FSX which was AWESOME, but have no idea how they actually did it (was pre-eyefinity).
I run Eyefinity at 6092 x 1080 across 3 screens with a 5870 1 GB. It plays most games very well, but with medium setting and no AA, I'm happy with it. However I would recommend a stronger graphics setup.
If you wanted to buy today I would get an nvidia SLI setup, 470s or 480s. Otherwise maybe wait for the 6900 series ATI cards to come out. You have to have 2 cards in SLI to run Nvidia Surround (Nvidia's Eyefinity). Goin ATI you only need 1 card, although I would recommend crossfire.
Would you recommend running 2 x ATI 6850's in crossfire? or even 6870's - I believe these are equivalent to 460GTX performance wise, which seems to be quite adequate if you read the article on multi monitor performance. (In SA the ATI's are about 10% cheaper)