Geforce 8800GTX upgrade....

Don't have too much info about my system being here at work but its a Dellxps that has a GeForce8800 GTX. I want to be able to upgrade my video monitor from an old gateway monitor to a large Dell Ultrasharp U-2711 27" monitor. Its resolution is 2560X1440. I went to maximumpc and looked at their best of the best but am not sure of what will run on my pc. Back in the day I used to follow very closely all the new types of hardware but having 5 kids and alot of responsibility has pulled me from my hobby and into working my rear end off. LOL.

So do you think if my computer could handle a GTX it could handle, lets say, a Sapphire’s Radeon HD 5870? Or what would be an appropriate upgrade to power the monitor?

Thanx a ton!

ps. if you need more info i can reply when I get home when I'm at the computer. Just let me know what I need and how to do it.