What size is you screen? I have a HD4850 in a XPS400 and It runs great.
The 220 is not a big jump from the 7950GT you would be better to go with the HD4850, You can get one for under $100 from Newegg.
Go here and look at the best GPU for the money.http://www.tomshardware.com/reviews/geforce-gts-450-radeon-hd-4850-gpu,2732.html
Look at the chart on the last page and look at the GPU and what tier they are on.
If you must go with nVidia go with the GTS 250.