^ wanting a top of the line means he doesn't care about cost
go with the ddr3, you have nothing to lose if you do not care. graphics card ONLY if you are going to do what the above has mentioned (games, videos, CAD). motherboard must simply comply with anything you place on it. hard drive is capacity based, but in terms of speed SCSI hard drives are the absolute fastest.
and when getting the central processing unit, please do not just look at the PROCESSING SPEED. also make sure to look at bandwidth and bus speed. those two affect performance as much as processing speed but it is not advertised as such.
if you have all three components (RAM, SCSI hard drive, and a server type processor) with high BUS speed (even if the capacity or PROCESSING speed is lower) it will ensure low error rate and a very smooth operation. good luck man.
remember, your computer is only going to be as strong as it's weakest link. if you have a sick monitor, but a slow OR weak video card, it will be pointless. and if you have a strong video card but the bus speed is too low, it is also wasted performance.
it was actually me who killed vasilli zaitsev, heinz thorwald, carlos hatchcock, and simo hayha