Please let me know if you think this power supply is enough for this SLI build and if not, please give me a recommendation. Also, I plan to overclock the CPU and GPUs. I will probably shoot for taking the i7 950 to either 3.8 or 4.0. Thanks for your comments in advance.
CORSAIR HX Series CMPSU-850HX 850W ATX12V 2.3 / EPS12V 2.91 80 PLUS SILVER Certified Modular Active PFC Power Supply
Corsair is a brand that has a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Some of the newer models come with a 7 year warranty.
How much does overclocking impact the power requirements? I mentioned overclocking my i7 950 to ~4.0 in my initial thread. It sounds like the 850 is plenty of power but I'm just curious how overclocking may impact the overall power consumption (if at all). Also, if I am within 100 watts or so of maxing out the power supply will it run louder and hotter. If I had more overhead room would it run quieter?
You will be nowhere near maxing out the PSU. A pair of GTX460's need about 20 amps. The CPU will need about 10 amps. A maximum overclock will increase the power consumption of the overclocked items no more than about 25%. So you are talking about from 30 amps to maybe 38 amps at 12 volts.
I doubt if the rest of the system will use 150 watts.