I purchased a K8NXP-SLI with a single Gigabyte 6600 video card. It was extremely loud. (I bought an SLI board with a non-SLI capable 6600 because I might want multiple heads later on.)
It's not an HTPC, but I value (near) silence anyway. I bought a "quiet" power supply from Antec, about $50; it's nearly silent. The noise comes from two big offenders: The fansink on the video card and the fansink on the north bridge.
For the video card, I purchased an Arctic Cooler 6 rev 2. Problem solved, though it takes up a lot of space!
The heatsink is more of a problem; I wanted to replace the fansink which is attrociously loud. The fan is really necessary; that chipset gets really hot! But it's under my video card, leaving no room at all for anything bigger than the stock. So I enabled SLI, and moved my primary video card to the secondary (PCIE x8 slot) leaving the primary slot empty. Now I install a Zalman ZM-NB47J on the heatsink.
The stock AMD CPU fan is quite acceptable except when at full speed. So configure lm_sensors under linux and off you go.
Now I'll have a problem when and if I buy a second video card, but until then, I'm all set. I've read that the difference in performance between x8 and x16 PCIe is negligible, so I don't think I've lost much. (And I don't play FPS games.)
PS: I won't buy another gigabyte board. This board has been a nightmare in support, BIOS updates, and compatibility with my maxtor SATA drive.
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