Found both these cool and quiet HTPC related links from HTPCnews

AnandTech reviews 21 silent / passively cooled video cards

"... The silent graphics card, a graphics card that is completely passively cooled, often using heat pipes and an oversized heatsink to eliminate the need for a fan to keep the GPU/memory cooled. The idea of a quiet or silent graphics card is appealing to many types of computer users, and many card manufacturers have realized this and are offering silent solutions. In the past, the only passively cooled video cards were slow entry level offerings. This is no longer true, and you can now get many mid range GPUs that offer reasonable performance without any noise output."

ExtremeTech builds a quiet, efficient Home Theater PC

"Nearly a year ago, we pieced together our Dual-Core Media Center PC. Since then, expansion of the HTPC ecosystem hasn't slowed one bit. The selection of faster and more versatile hardware such as motherboards, graphics cards, tuners, and cases has multiplied along with the availability of free and paid-for software solutions. Microsoft continues to refine its much-improved Windows Media Center Edition 2005. BeyondTV, GB-PVR, MythTV, and SageTV have maintained loyal followers of their own. In the realm of consumer electronics, more flat panel TVs include DVI and VGA inputs enabling them to handle double duty as both a TV and PC monitor."