but i5 is a dead zone..... no luck if you would choose to upgrade later.... 1366 is better for a longer run.... don't get me wrong 750 will probably do the job but maybe in da future 6 cores will drop in the price so he'll be ready for an update.
1) the i5 will be plenty to run games out quite a few years (look at teh Q6600, when OC'ed to 3.2 GHz it can still game just fine)
2) then stick to the AM3 platform for longevity since LGA1366 is getting replaced as well
3) there are few games that use Quad cores effectively (let alone 6, though BF:BC2 can use up to 8!)
4) the 5 cores will not drop in price to a reasonable level (look at the Q9550, still expensive even on a dated platform)
more than likely it isn't going to matter since any of these CPU's are powerful enough for the foreseeable future
EDIT: i would switch to Win7 64 bit