Probably sticking with a single 6950. I don't really see much of the point in running a Crossfire configuration since most games I play are running at max settings on my 5770, and even Crysis 1 runs smoothly on high on it.
Shub: I was looking at the SeaSonic models on Newegg.ca and saw a couple along with Corsair ones that were all pretty highly rated, though there isn't a feature to select decibel rating of the fan on it unfortunately. But I am not sure if the models you suggested were in my search options. I'd prefer modular as well, I am not a big fan of the single cable with tons of wires inside it