Hi im about to buy Mac Pro and I have a question re Ram upgrade options. So the Mac Pro comes with 1g in 2 x 512 sticks. Id like to beef it up with a few more Gs or ram. Can I use new 1g sticks along side the original 512s?..... I ask this because I think I heard somewhere that all the ram sticks need to be the same size. Is this true? or can I put 1g or 2g stick in with the original 512s? Lookforward to your responses Thanks!