Not to be confused with fact.
If you want to run gpu's in parallel it's best to have a matched set.
The farther you move away from the "matched set" the more fuss-in might be needed to get the mix to play nice together.
I'm not aware of rules for gpu mix+match.
I'm really not very familiar with installing two discrete graphics cards in the same PC, but the case is, i have a nvidia gtx 480, and rather than selling it, i thought of keeping it with new one which is the gtx 680, what's the odds of having them in SLI connection, and if not how can i be using them in the PC, what's the situation thn, and the regulations for different multiple cards usage in the pc