[PLAIN]EVGA GeForce GT 520 (Fermi) 01G-P3-1526-KR 1GB 64-Bit DDR3 PCI Express 2.0 x16 HDCP Ready Video Card - Newegg.com[/PLAIN]
Its $64.99, newest version of the GT series, and my brothers computer has the same exact CPU with the GPU I showed you and he can run source games fine; Also, it's EVGA. The only problem your going to have is that crap PSU... If you have the money, I would recommend that you try upgrading your PSU to at least 350W+ before buying a new GPU, or you might have some overheating problems later on. (Btw, if you are going to buy a new PSU, try buying ones that have good ratings and aren't SUPER cheap like this one: SeaSonic SS-350SFE 350W SFX12V V3.1 80 PLUS Certified Active PFC Power Supply - Newegg.com)