Thinking of buy a CORSAIR TX SERIE PSU 750W 140MM FAN ATX 80PLUS. Have read the test at Hardware Secrets and they was discovering a high electrical noise at the +12V rail then "where we were pulling 610 W from this power supply, noise level was at 60 mV at +12V1 and 68 mV at +12V2... With the power supply operating at its full load, noise level was of 90.6 mV at 12V1 input and 103 mV at +12V2 input".
Every output voltage will have some fluctuations in the actual voltage being output. If you hooked up a volt meter to that PSU at full load, you're 12v1 might read something like 12.04v. But if you use an oscilloscope, you can actually see a little bit of bounce in the voltage. Those graphs for the noise are the output from the oscilloscope. So you can see the 12.04v would actually vary between 12.037v and 12.043v. ATX standards say the variation can't be more than 120mvs, so 60 is well within specifications. 60 and 68 aren't bad numbers, but there are some better out there. Sometimes you'll hear the term clean power and the lower the noise, the cleaner the power.
The Corsair 750TX is a good choice. It will serve you well.