Using the GTX 480 in an SLI configuration is going to supply awesome gaming performance. Along with that performance you are going to get a LOT of heat and a lot of noise. There are just no two ways about it. GTX 480 SLI is hot and loud. Without the air conditioning on in my house it raised my office temperature by over 10F overnight while leaving a 3D game running. I can hear the GTX 480 SLI downstairs from my office. I can close the door to my office and hear it running. It makes a lot loud sound. It however is not terribly annoying. The sound during normal usage is not so shrill that it is terribly annoying, but you will hear it. If you however have a high ambient temperature in your house or are putting two GTX 480 into a chassis that has an in-case ambient temperature above 95F or so; be prepared to hear some real racket. Even with the SLI set up well ventilated, I could still hear the system with my headphones on. Sitting 4 feet away, 480 SLI is going to pump out 55dB under load; and that is a best case scenario, unless you live in Alaska.