Fast and quiet HTPC video card

[fuzzymath10]

My HTPC (or living room PC; see second machine in sig) has a Radeon 4830 installed. However I'm looking for better codec bitstreaming and compatibility with decoding video. I believe new 6000 Radeons won't work with Server 2008 R2 without hacked drivers because new Catalyst revisions won't install on server OSes. What nvidia options have at least the same level of performance with possible lower idle use, and quiet/passive cooling? Can anybody confirm that nvidia drivers don't have the same limitation with server OSes?