nVidia and ATI cards don't typically play well together. You'd want to stick with similar brand cards, at least. If possible.
Do you think it's risky to my rig to install them both and give it a shot?
I'm curious, what coin are you all mining with graphics cards?
Gonna be trying Litecoin, CornedBeef.
That's cool. I've got a few litecoin.
I'd try your hand at a non-Scrypt coin. Perhaps one of the X11 coins like Darkcoin. Scrypt is really hard to GPU mine anymore tx to ASICs...
Not really, those coin's difficulty are really rising up high. You still have to cover electrical and hardware cost. It might not be possible to ROI.