I have a dedicated computer with Media Center for all my "DVR" stuff. Although Media Center is a little out dated compaired to other programs, and I have never used this set-up for HD, I would consider this option over the boxes the cable companies try to sell you.
It's not cheap. My computer set up the way I wanted it cost over $1400.00. But, I geared it more torwards a music set-up than a TV rig. The sound card alone was over 300.00 plus all the fiber optic crap. But the nice thing about it is, I have 4 hard drives, an external 100 for music only, an external 300 for recorded tv, an internal 80 for internet stuff and pictures, and an internal 40 for back-up junk... I few of the nice things about it are that it takes the place of a DVD player, CD player, DVR, radio receiver, has all your music loaded onto a HD, ability to download music right off the internet to your PC, ability to burn music CD or DVD's, no monthly DVR fees, software updates, and works really well with home theator systems. Then, if you wanted to get really fancy, you can add something like a sling box and watch your TV anywhere you have an internet connection..
You could probably build a super fast Shuttle PC for like 600.00 or 700.00 and the thing would be no bigger than a mac-mini. You can get really creative with all the options avaliable.
