but first try this without SLI. there is not a single reason in ubuntu as to why you need to use SLI. Crysis is the only game where SLI makes some sence. Doom 3, Quake 4 and Unreal Tournament 3, the three bigshot games on Linux, can stay comfortable without an SLI setup.
and as I told you before, please wait till hardy comes out if you want to install ubuntu. Its only maximum 50 days away.