I think I know the answer, but I just want to confirm before I actually spend money on this. I currently have 2GB's of RAM in my mac pro, 4 x 512MB. Am I correct in assuming that in order to keep my quad channel RAM performance, I would need to add 4 of the same type of DIMM's, so either 4 x 1GB, or 4 x 512MB? Which would then bring my total to 6GB or 4GB. Thanks!