Greetings, I'm looking to outfit a new Mac Pro with 4GB of RAM. At places like OWC and Datamem, the difference between buying 4x1GB and 2x2GB is fairly minimal. Would there be anything wrong with buying the 2x2gb (putting that in one riser) and sticking the stock 2x512MB from Apple in the other riser for now (for a total of 5GB)? The 2x2gb pair seems to have more longevity to it, because I can always hold onto it if I choose to max out the machine's RAM. Whereas with 4x1GB I would have to sell off that pair to max out the machine. Any opinions? I've also heard it is ideal to have matching pairs in each riser (a pair of 1gb in one riser, and a pair of 1gb in the other)... but not essential.