Your sig rig? Don't trust the calculators too much. You really don't need 800W.
My best bet would be the PC Power & Cooling Silencer 750W
for $199.99, which has a single 12V rail of 60A. That should be more than enough.
Again, I run my rig of an FSP Epsilon 700W, and mine seems to draw more power than yours.
And if you include two high-end DX10 cards.... there simply is NO PSU right now (including the 1KW units) that can handle a pair of 250W GPUs are the moment. The pair would require 500W, all on the 12V rail. That's 42A on the 12V rail, and even the PC Power & Cooling 1KW Unit does NOT deliver that on the rail dedicated to graphics (which is 36A)
The best solution is the 750W, single rail PSU, and simply add a second PSU, also single rail with about 25A or so, for the second video card./
This all assuming the DX10 cards actually draw from the PSU. I've heard things about exterrnal power and so on.