hrmm..the 7950 is old now. take a gander at the 8600. it spanks even ati's x1950(and the 7950 for that matter) and only needs a single card to do it. SLI is overrated. Go with the 8xxx series. In single mode they crush everything out there..and the 8800 can beat most ati x-fire setups too. Also don't use the RAID in the mobo bios. Use the raid inside windows..you'll be glad you did(google FRAID). The statements in there are just as true for windows. Which case do you have now? Do you have more than just the fan for the psu(aka are there any additional fans in the case itself?) Also RAID1 will protect you against data loss form hard disk failure..NOT data loss due to virus infection, spyware, or fat fingering..

Remove one of the hdd's and go for an external hdd. 80 gigs should suffice. Only backup important data(documents, music, saved game files) not the entire programs. Put that extra money towards a better vid card or better cooling or better psu(psu, cooling, vid in that order). with 32 bit vista you'll only see 3-3.7 gigs anyways(depending on how much ram your vid card has) so stick with 2 gigs. That being said, this isn't a bad system..don't get that impression.
Frankly that's a good rig. If you can finagles the components a bit great..but that's a solid machine that will serve well. If you want to go with that machine..it's nice and it will serve you well. With a bit of effort though it can possibly become even more beastie..<G>