I just bought a mac pro from B&H (delivers today) - 4-core 3.0 ghz/X1900 with one gig of RAM. I want to upgrade the RAM to 8 gig. From Crucial, I note that 8 gigs of 2-gig x4 is $840 vs 8 gigs of 4-gig x2 at $1749. Looking at RAM from Crucial -- my question..assume that I pull the the two OEM 512's...in getting to 8 gigs there some substantial advantage to using as few DIMMs as possible? IOW, is it worth twice the cost having two of the eight RAM sockets filled for $1749 as opposed to 4 of them filled for $840? Is heat an issue? Timing? Other reasons that fewer DIMMs would be substantially better? Worth the $800+? extra? And...if I use 2-gig DIMMs x4 (my preference, obviously), I'll still have 4 open sockets in the 2nd riser. Any problem with slapping the OEM two 512 meg DIMMs in that configuration for a total of 9 gig RAM?