Upgrade Compaq Presario SR5707C Desktop

One thing that makes the 7850 better then the 965, is that I already own one. What I am trying to do is not spend money I dont have. What I do have is (one Compaq Presario SR5707C Desktop PC with AMD Athlon X2 4850e - ADH4850IAA5DO Two DDR2 2GB, GeForce 9600 GT and 450w power supply) This is the PC my son uses, he games online and watches online video.

I also have a HP Pavilion Media Center TV m7640n Desktop with AMD Athlon 64 X2 5000+ - ADO5000IAA5CZ
, Four DDR2 1GB, GeForce 9500 GT and a 500w power supply. I play some online games but mostly run CorelDRAW Graphics Suite X5

I also have a AMD Athlon X2 7850 Black Edition - AD785ZWCJ2BGH and a second GeForce 9500 GT

On the Compaq Presario SR5707C Desktop I will add a ASRock A770CrossFire and a AMD Phenom II X4 830 - HDX830WFK4DGM

Providing that will work, On the HP Pavilion Media Center TV m7640n I will add a ASRock A770CrossFire and one of the CPUs I already own which one would be best

AMD Athlon X2 7850 Black Edition - AD785ZWCJ2BGH


AMD Athlon 64 X2 5000+ - ADO5000IAA5CZ


AMD Athlon X2 4850e - ADH4850IAA5DO


Thanks :pt1cable: