I got a private message asking for how I fixed the SATA drivers issue, so I figure I may as well post it here so others can benefit. This thread has instructions on how to install the 790i SATA drivers. Install those and everything should work fine from then on.

XavierMaxx: Good to hear you're getting things working right! What kind of card are you going to be running in SLI?

I've been fiddling around more. I removed one of my cards and ran 3DMark06 and Crysis. I noticed no slowdown in Crysis and I recorded a score of 12,979 in 3DMark06 (5391 SM2.0, 5489 HDR/SM3.0, 4123 CPU). Upon adding the second card back in and getting everything installed, I ran 3DMark06 again while forcing AFR2 and got 14,428 (5319, 7096, 4128). I got a slightly lower score than with only 1 card installed when letting the application itself decide what to use.