Dual Core @ 2.8GHz, 4GB and a card in the GT8600 range would be the minimum spec.
The RAM upgrade will be beneficial.... I believe the HD3000 on the Celeron should be right in the same ballpark of a GT8600....
The CPU could actually be the greatest limiting factor.
I'd expect 720p (perhaps with some resolution scaling tweaks) @ v.low type-presets to be your best chance.