User's data at this point:
* PSU actively drawing 500W: »Re: loud corsair HX1050
* System consists of the following, minus one video card: »Re: loud corsair HX1050
* Core i5 is overclocked to 4.3GHz: »Re: loud corsair HX1050
* All the above could explain about a 400-500W draw under full system load given those specs.
My guess is that the issue has nothing to do with PSU load at all, but probably temperature. Many PSUs will increase fan speed based on temperature, read from a thermistor inside the PSU itself.
There's really not much you can do about this other than try to decrease the overall temperature around the area of the PSU, or to purchase a different brand or model of PSU that might have a fan that's less audible (I've tried to warn people here about how loud PCs are getting these days, sigh) or logic circuitry that doesn't kick the fan on a higher speed until a significantly higher temperature than what the HX1050 does.
I'll use this opportunity to state something clear and in bold: do not consider a fanless PSU given what your system consists of. This will only make the situation worse.
I've had the pleasure of using one (rated for 450W) and I could not believe how hot they got under normal load (I had to wait about 20 minutes to remove the PSU from the case, else my fingers would have suffered 1st or 2nd degree burns -- no joke). The increase in PSU temperature has a direct and circular effect on temperatures of the case and all components.
Stick with something that has a 120mm or 140mm fan and advertises very low noise. I would recommend trying Antec or Nexus/Nexustek PSUs. You will need to spend a lot of time looking at full specifications, specifically fan noise ratings. I would suggest a 750W or 850W PSU, cease the overclocking, and stick with just one video card/GPU indefinitely.--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.