Celeron is a NO NO. You might as well use onboard graphics or get one of those 5500FX video cards for 19 bucks if you do that.
Its like putting Corvette racing wheels and tires on a 100hp VW if you get a Celeron for gaming.
Get an E2160/2180 and a 9600GT. You wont be disappointed in the 9600GT. I have both of these in my media center setup and it scored almost 8000 on futuremark06. Not bad for a budget build.
The 3870 should be a comparable card for the money so either should be a good choice for your situation.
My friend has a 9600GT in his system and he runs 2 32" monitors with no problems and we played F.E.A.R. with no hickups.
If you cant afford to get decent hardware then wait until you can. Dont flush your money down the toilet getting half baked hardware to game with...