You can run games faster and more efficiently on XP pro, its a whole lot less demanding than Windows 7 and is easier to use IMO. You do lose security that you get with Windows 7.- Operating system will be Windows 7
XP is less demanding to run, so there is less of need for power. All the power your talking about putting down in the computer will equal a beast! My friends laptop with 7 has 6gb of ram in it, its built for gaming and has an ATI graphics car and it plays games only slightly faster than my computer. Its an eMachines case, with some random motherboard idk what kind, 1gb of ram, a 60gb HDD, 1gb of DDR1 memory, and a 256mb amd ATI Radeon X700 pro graphics card.