[Onboard]
Procy: AMD Phenom X3 Phenom X3 8450 Tri-Core = 4670/-
Mobo: Asus M3A = 4950/-
[With a Card]
Mobo: Asus Nvidia M2n68-AM - 2250/-
Procy: AMD ATHLON X2 7750 Black Edition - 3300/-
[or Athlon 64 X2 7750+ 2.9GHz 3550/-]
GFX: Palit 9600GT 512MB DDR3- 5400/-
[If you can extend a bit Palit 9800GT 512MB DDR3 - 7075- ]
Since you said gaming, I would suggest you go with a better GFX card over the better Processor. The 8600GT is not too good for gaming.