Admittedly, Sabayon has not been my distro of choice due to ongoing mouse problems. I use a logitech marble mouse and I'm a lefty. I've used 3.4e, 3.4f, and 1.1 "Pro."
Anyhow, I keep a Sabayon cd handy. This machine I'm on is a AMD 64 3700+ Socket 939 CPU, ASUS A8N-32SLI Deluxe mobo, 1 gb RAM, 2 X 200 gb SATA hdd's, 1 X 250 gb PATA hdd for additional storage and 2 X XFX 7600 GT video cards in SLI (at least in WinXP). Current OS's are WinXP and Sabayon Professional. Nvidia drivers are off the install DVD. They seem to work fine.
Under the Nvidia X server settings, both cards are recognized. Does this mean both cards are in use? Temps are read for both cards. I was expecting a "check" box somewhere to enable SLI but didn't run onto one. I didn't think that SLI would be something that would "just work."