I wanted to put my vote in for Media Portal as well. It can run in a client/server config which is basically what I do (No TV tuners, but all my media is on my file server).

My front end is also my only Blu-ray player. For Blu-ray playback remember, there are still many bugs to work out for the same features as a standalone player. For instance the only way to bitstream HD audio currently is with Asus' Xonar HDAV 1.3. (Since the Auzentech card isn't out yet.) Unfortunately last I saw this was coming at the price of reduced picture quality. So I'm currently just adding standard 5.1 S/PDIF audio to my HDMI connection providing me with standard Dolby Digital and DTS, none of the uncompressed HD audio. There are plugins for Media Portal to seamlessly launch PowerDVD or ArcSoft's TotalMedia Theatre, so it can all be done from the one interface. I do use AnyDVD HD as well as it eliminated all non-playing discs.

My front end is:
Intel Core 2 Duo E4500 (2.2 Ghz) (Zalman CPU fan)
2 GB Ram (Not enough for both Media Portal and PowerDVD to run at the same time on Vista, but it's my current mobo's max.)
LG Blu-ray/HD DVD combo drive - Which included PowerDVD 7 Ultra
Fanless MSI GeForce 8500 GT
100 Mb LAN ->Plenty to stream HD video from my file server
80GB IDE hard drive I had lying around.
nMedia PC case that included an IR port and remote.

I can only hear it when everything is off. I've definitely spent quite a bit on it, but I'd estimate I'm still under $1k.