The GTX 650 requires an additional 6-pin power cable hook up from your PSU which you do not have. The best you can do is the HD 7750. It offers performance close to the GTX 650, but does not need this hook up and does not use as much power. Of course, you can always upgrade your power supply to accommodate higher-end video cards if you want, but your old Pentium D will hold you back. For just $25, you can upgrade to a Core 2 Duo E6600 off ebay which is what I did on my 745 SFF.