Shadow makes a good point about Sandy Bridge, if you can wait. And easymoney makes a good point about the mobo, too. I'd go for a full ATX board. (Edit: If I'm not wrong, micro-ATX boards usually cost a bit more.)
RPM is definitely one of the factors that determines the speed of a drive; what I meant was that this 3-platter 5400RPM drive is just as fast as any 4-platter (500GB/platter, 2TB) 7200RPM drive. What you listed is a 3-platter (500GB/platter) 7200RPM drive, so it is a bit faster than the F4, but value-wise, the F4 is a much better buy. If it's for storage, then, considering the price difference, the difference in speed is negligible. Also, don't forget that 5400RPM drives run cooler and quieter than their 7200RPM counterparts.