I do like how you think and I do the same thing with getting what I want to put into my computer no matter what anybody else says. I currently have three GTX 580's in a three way SLI and I could get a fourth if I wanted to. The reason that I don't is because I notice that after two cards there really wasn't that much of a noticeable difference in the visual aspect of viewing everthing. There was an increase in the fps which I'm sure there would be if I got a fourth but I'm thinking that I wouldn't notice anything being better and believe me if there would be a noticeable better visual of the games then I would do it. So in your case I would get three and then maybe something outrageous with monitors. Maybe two or three 30" ones or a six screen setup or one of those new cinema screens that are one continuous screen but with the size of three with no bezel.
http://www.youtube.com/watch?v=ZWivZEtH6-c&feature=related
http://www.youtube.com/watch?v=UixSNqED4pc&feature=related
http://www.youtube.com/watch?feature=endscreen&NR=1&v=-yvakLCwbz4
This would be the ultimate!!!
http://www.youtube.com/watch?v=dOY2lREuwjU&feature=related