I recommend getting an ASUS P6TD, its a newer version and i never had a problem with asus...or gigabyte, both are excellent. I don't see why you would get a 850watt for that. A 600-700watt good quality PSU would do fine. I guess you plan on Crossfiring or SLI'ing. If you are spending a lot on your system, get Mushkin Enhanced Redlines 6GB Tri-Channel. They have 1600mhz and the best Latency for thier frequency at CL6. Also, are you planning on Overclocking?
Not planning on overclocking, the memory is also not available any more on newegg, is there anywhere else to buy it? I'll be buying another 5870 in a year or 2 when they drop price but until then i wont be crossfiring.
A cooler master V8 or V10....V10 is pretty expensive and its for the extreme overclovkers and is quite overkill, but a V8 is near the top of the chain. Paired with good thermal paste, a V8 will cool amazing. I have one, I know.