Sorry to hear about the noise issue. I have had this in the past with a few builds and various sound cards. After long and maddening process of elimination the issues were caused by grounding or magnetic interference thrown by the video card. One grounding issue was caused by a motherboard mounting post that was contacting a solder joint which overlapped the mounting area slightly and was touching the mounting post. I could not see this till I took the motherboard out and looked at the bottom. Another issue was caused by a cheap nic. The video card did cause interference when it was too close to the sound card. I keep my sound card in the very last slot and the video card in the very first slot now. I don't run SLI anymore. The issue I had was while running SLI. To confirm, is the buzz you're getting exactly like the buzz you get when you have a ground loop issue on the power source for amps? If so, it's probably grounding somewhere in your box. If the noise is variable based on load on the video card then look there first. Run a graphic intensive application or game and get the card hot and ramp up the fans. If the noise goes up then you may not have to check the entire box for unwanted grounding. Mess with the video card(s). I also remember reading that having a sound card in close proximity to platter hard drives can cause magnetic interference as well. I have never seen this. There may be other explanations but this has been my experience. I run an i7 920 with gtx470 today with no issues. I hope that helps.