Dell will sell me a Dimension 4100 with 133Mhz SDRAM and a ATA-66 hard drive for $2178. For $400 more, they will sell me a Dimension XPS B with RDRAM and a ATA-100 hard drive. Can you tell me what the extra $400 buys me? How much better is RDRAM over SDRAM and ATA-100 over ATA-66? Both desktops come with a 1GZ PIII processor but the motherboard is unspecified. Mike Bresnahan