Hi gang I'm going to be ordering a BTO Mac from Apple. I'll be using it for photo retouching & Aperture. I have read Aperture loves RAM and works best with 3-4 gigs of RAM. However, I don't want to spend the $$$ on expensive Mac RAM. My thought is to get the BTO with the stock Apple RAM configuration of 1 Gig (2 x 512MB) and then upgrade to 4gig total with third party RAM. My question is I heard the mac pro's should have RAM installed in matching dual pairs.... so, if I want 4Gig of RAM I should buy 4 x 1GB sticks so that I have two matching pairs, and then sell off the 2x512MB from Apple (because I shouldn't have 5GB in the computer?). Is this how it works? Or, could I keep the 2x512MB and match it with another pair of 2x512MB (third party). And then buy two more 1gig sticks? Any advice is appreciated!