what is your budget, that would help me.
second in your games do you want to to play everything on high ?
most people are going for the E8600 until I7, if your not going with crossfire or SLI your best off with a p45 chipset with a single PCIe slot
for crossfire you will need 2 PCIe slots...again P45 can handle that easy but its only 8x/8x electrical, all other times with a single card its full speed.
if you want SLI than you would need to look at 750i-780i if going DDR3 790i
if you want to go full speed ahead with crossfire than get a X48 chipset mobo
for windows vista you will need 3Gb of ram unless you are going 64bit than you may have over 4Gb but thats over kill
yes you can get P45 chipsets with DDR3 memory support and same goes for x48 infact they are mostly DDR3 but I don't think you need DDR3 at this moment in time so that save money:P