Honestly, once you've tried three, you'll never want to go back to one or two - i love it that much.
My only gripe with three is that you ideally need SLI or a beast of a GPU to run games on it smoothly. Far Cry 3 will now only run at like 23fps, bf3 30fps and so on. You should be fine with SLI 670's though! (Ultra settings)