Motherboards don't have any difference between brands of graphics cards but they differ if you can install a sli or crossfire configuration.
But i recommend getting an Amd chipset motherboard, you can find cheap ones that have great performance.
Also i agree with Soleron, you can buy medium range graphics cards and get excellent performance in starcraft. With other pc games you will also have great performance since most pc games are ports from consoles.
Get a 550 W to 650 W power supply and you will be fine. Unless you will be overclocking or have in mind for a future crossfire configuration. I have a thermaltake 750w power supply with 2 8800gts, an overclocked phenom 955 and works perferctly, i have if for 3 years now. I recommend thermaltake power supplies, there are also other good brands but i haven't tested any.