I could be wrong about this, but even if it was possible to SLI a GT and a GTO, I would imagine that they would default to running as the lowest common denominator. Essetnially, you would turn your GT into a GTO. Still might be worth it to you though because I'm sure two GTO's would be faster than a single GT. If you have two the cards and an SLI mobo, give it a whirl and tell us what happens 🙂