Why are you buying that cpu? Resolution you intend to play at? What video card are you getting? As for mobos i would recommend Asus or Gibabyte brand mobos

If you dont want to spend on an i7 core system i would recommend

Gigabyte GA EP45 UD3P to go along with a Q9650 easily can be oc to 4.0GHZ and call it a day

/my 2 cents

I dont think that the mobo and the OS are related to each other whatsoever, so am pretty sure you can install a 64bit OS in your system.

If you install a 32bit OS the most RAM it will detect, I believe is 3.5GB. A 64bit OS will detect 4+GB

I dont know if those games will run on that comp but from that list the best games are imo:

COD4, Fallout 3, L4D, Crysis , HL2, Bioshock