comeon guys, back to the matter at hand....
Dude, u DEF want to water cool instead of SLI. You'll only get a 10-20% increase in performance for a 100% increase in gfx costs. thats a text book example of diminishing return if i ever saw one.
you can get a water cooled system for your CPU, RAM, and GPU (all in one check out http://www.frozencpu.com/ex-wat-94.html
) for alil more than a 7900GT and tweak it out hardcore. you'll be gettin like 50% +/- 10% faster clock times for each piece of hardware. now you tell me what you should do. yeah, thought so.