Corsair HX620 coil whine and unstability issues

Hello!

I own one HX620 PSU for about 4 years now. About one year ago, i bought a wireless razer gaming mouse which annoyingly kept freezing during games, requiring me to unplug it and replug for it to work again. Using it in wired mode however sold any issued. I rma that mouse, and razer said everything was fine, and i should check if my motherboard was supplying enough power to usb ports, and sent me a new mouse either way. New mouse also had the same symptom, so i tried it on another pc, and it worked flawlessly. So i blamed the mobo.

Last week, I replaced my old stock HD4850 with a Sapphire HD7970 Vapor-X and I also got a new Asrock mATX board and a Silverstone FT02 case. I plugged everything and once i hit the first game i noticed a loud electric buzz/whine coming from inside the case, which get louder as the fps climb up. Vsyc to 60fps/60hz reduces the noise but its still noticeable, Vsync to 120fps, makes it extremely loud, and no vsync during a menu, when fps go to 800-900, results in a unbearable noise, and shortly after the gpu stops responding and screen goes black. Reboot brings it back. PC also shuts down randomly during high fps games.

I immediately blamed it on the gfx, and thought i was unlucky to get a bad sample. However once I opened the case I immediately noticed the noise was not coming from inside the case, but rather from its top/back. Remember the FT02 places the psu so that the large fan side faces the back of the case, and the perpendicular smaller side in which you plug the outlet cord, faces up. Once i get closer and placed my ear next to its vents, it was evident the noise was indeed coming from inside, more clearly from the larger fan side!

So It came to mind maybe its from the PSU, but its the new GFX or mobo causing it? I then decided to replace the GFX with my old HD4850, and the noise pretty much disappeared, still there was something there i had never noticed before, maybe the new case having the psu fan turned twards the back of the case makes the noise more noticeable, but it was there. I then, launched wow menu, and fps went to 200 no more then that, that electrical buzz is noticeable when my ear is close to the psu, but nothing i will notice during game play. So i decide to slightly overclock the card, using amd's software. And then it returns, during the ams catalyst overdrive benchmark, the noise comes back, and though its not as loud as with the 7970, its still loud! I also made a test run with my old mobo, and results were the same.

I should mention that with the HD7970 the buzz is always present. I can discard it while on idle, but i hear it while playing 720p movies, scrolling on the web, etc, and gets louder as i load the gpu. With the 4850 i only notice it really close to the psu, but once i oc'ed the gpu, or ran a bechmark that will load my gpu and still yeild high fps's (like the one in amd overdrive), the noise is also there.

I also tested this GFX on a friends computer, he runs a 2500K, asus pro-v, msi gtx570 and another HX620. Replacing his GFX with my 7970, revealed no noise what so ever, even during wow Menu, were fps when to around 1000.

I'm guessing this problem was always there, I just never noticed because my system never really put any kind of load on the psu, about 160W drawn from the outlet at load. Now it draws almost 3 times that I also had never ran the amd overdrive benchmark, because i never oc'ed the GPU. I believe the more power hungry HD7970 revealed it and made me test the psu for things i never really had to, it also would explain the issue with my usb wireless mouse and why it never worked fine for me on this pc, but worked flawlessly on others.

My question is, what can i do about this?