Need to upgrade my old 9600gt

[Creepingdeath1977]

Hey guys I've got an MSI geforce 9600gt I've used for a few years and I'm looking to upgrade it finally, but I would like to avoid upgrading my PSU so I was looking for a good upgrade for under $150. I play Hawken and a few other titles on my PC but I've really been out of the loop when it comes to Vcards for the past couple of years.

I would like to avoid upgrading anything else besides the video card if possible.

Cliff Notes:
Phenom II 3.ghz
600w PSU
Gigabyte PCI express 2.0 board
2gigs Gskill DDR3
geforce 9600gt-needed to upgrade

Thanks in advance.