Ah I see, and good point. I'm not actually sure of the current makeup, but I *think* it will be 4 x 2GB..
Looking at crucial.com, they say the stock XPS 630 has 4 slots and a max 2GB per slot, so looks like I'll be at max anyway - I'm presuming it's 4 x 2GB DDR2 PC2-6400 (800MHz), even though the Vista Home Premium 64bit o/s *can* work with up to 16GB. I guess I could replace them with 4 x 2GB DDR2 PC2-8500 (1066MHz) though.. would it be worth the effort for ~$150?
By disk set you meant the o/s and drivers, yes?
*edit* - apparently unless I clock the Q9550 CPU of 1333FSB up to over 1600, it won't make much difference using 800MHz RAM or 1066. Additionally, if I downgrade the o/s to XP (32bit), then anything over 4GB RAM does not get utilized by the o/s anyway, so looks like I'll be good on the 8GB 800MHz RAM they are supplying with the PC already.
*further edit* - ok damn. Apparently the 'stock' motherboard is a proprietary 650i, which has 2 graphics PCI slots, but each only has 8 lanes. That's fine for SLI with say GT8800 which max around 80GB/s, but the GTX280 is a single card which really needs 16 lanes, so the card is going to be effectively bottlenecked to around 80GB/s, instead of the 115-160GB/s the GTX280 can handle.. that's just silly. What a waste of resources. Wonder if Dell will let me upgrade to 750i motherboard for cheap (has a 16 lane PCI slot)...
And even furthermore, the mobo can't handle PC2-8500 RAM; apparently PC2-6400 is the max, but they can be clocked up to 1066 on stock setup anyway (according to Dell), so it looks like I am definitely at the max as far as RAM goes.