Now if only I had the cash for all of that
I would think that each CPU ought to get it's own loop, if you want to run a multiloop system. The CPUs should have better cooling than the video. Not like it
really matters, but that's the way I would do things. Maybe you could have one loop cooling the procs and another cooling the video, chipset, and memory (if you could come up with some kind of block for them.
As far as computer-specific radiators go, the best performers are the OCWC Big Momma (my personal fav,) the Danger Den cube, and the BeCooling cube. OCWC Black Ice are also good but smaller and, obviously, not quite the performers as the rest. Maybe a few Black Ices might work?