I don't know that the PC will replace the DVR very well. The only DVR software I know of is MythTV which is a Linux thing. HP doesn't say whether these boxes have video inputs, they don't say whether they have surround sound out, they don't say whether they have HDMI out.
Shrug, I dunno. It looks like a good product. But any computer can act like a server; I use an old PC with Linux on it as our "public" drive. Most computers can browse on the big screen.
You might take a look at the
Roku-HD as well, that might be more what you want, especially if that receiver has HDMI inputs.