9600 GT is a good and powerful card that performs slightly better then 4670
Toms Hardware recommends both 4670 and 9600 GT.
PSU is just not good for both these cards,
I am sorry, didn't read it before.
You need atleast 400W PSU to run these cards
But you can still buy 4650 and play all games with maximum settings at 1280x1024
But I think you should upgrade your PSU to atleast, atleast 400W.
Think twice before buying a new card.
I strongly recommend you to wait a bit, arrange some money, upgrade PSU and Go for 9600 GT or 4670.http://www.newegg.com/Product/Product.aspx?Item=N82E16817162018http://www.newegg.com/Product/Product.aspx?Item=N82E16817171031http://www.newegg.com/Product/Product.aspx?Item=N82E16817339012http://www.newegg.com/Product/Product.aspx?Item=N82E16817170017
Pick any of these.
Some are cheap so take a brief look.
All of these have good reviews and ratings.