I was tired of running my file server on wireless but I didn't want to have a computer case sitting in my living room. My solution was to build my server into a cabinet that sits a foot or so from my entertainment center and router. It's out of sight!
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Nice stealth setup there. Definitely a possibility for a home brew PVR.
I've done something very similar - I installed a computer in a side cabinet in our entertainment unit with a TV card to run our pay TV over Ethernet to replace a wireless transmitter setup that interferes with our wireless (for the most part anyway - I'll retain the transmitter for IR until I figure out another way). I had a board in there but the TV card I had was missing a vital cable to connect to the audio outputs on the set top box. On the plus side, I have in-principal wife approval for the build - it's out of sight so she doesn't even think about it.
As for digital TV I plan to use a HDHomeRun. AU$160 and it hooks straight into Windows Media Center anywhere you can get a network connection (which, thanks to wireless, is anywhere).