What is your budget?
Good cards for 3 monitors are ATI 5870 and 5850 (Eyefinity Technology).
budget is upto 150 -175$. but would prefer Nvidia cards. do any of the Nvidia cards support 3 monitors? Alsoo how can three monitors be connected on an ATI 5870. I would like to run a DirectX based virtual world on the three of them.
The easiest route is to buy two cheap $50 video cards. ATI vs Nvidia doesn't matter, since all you care about are the display outputs.
If you want a single video card, you'll need an ATI 5000 series, but you'll also require output adapters since . Tom's did a review of the 5450, using a 3 monitor setup. You'll also need to grab an "active" DisplayPort converter, which today can be found for under $25 if you know where to look. http://www.tomshardware.com/reviews/radeon-hd-5450,2549...
No Nvidia cards support 3 displays from a single card, you have to go with multiple cards for 3+ displays
Thank you so much for the link, it was really informative .It seems that the center screen in the 3 display arrangement feels stretched. In case i go for multiple display cards for the 3 displays, will it be possible to render a single instance of directX virtual world across the three monitors?