Okay, I'm up and running.
I still need a case and a soundcard, but as I had the rest of the bits I put it in to a spare tower case and got the software installed.
There's nothing remarkable to be honest, it just worked. I presume I might have some problems getting the resolution right once I connect it to my plasma (TH50PX60) , but, it worked fine whilst connected to my monitor (which will accept 720p over HDMI) so I assume it won't be too difficult.
The final spec looked like this:
- MSI P6NGM with on-board Gigabit NIC
- Intel Core 2 Celeron @ 1.6Ghz (I think, I didn't check and BIOS screen doesn't stay on long enough via HDMI)
- Gainward 8400GS 512MB HDMI out
- 250GB SATA Maxtor (all I had to hand, content will be streamed mostly)
- Samsung DVD-RW, I'm going to pull this when I build in the new case, just made the software install easy (It's bankholiday weekend, I can be lazy!)
- 1GB of RAM
I initially went with Linux Mint, but, I still can't really get away with the Ubuntu way, so, I ditiched it and did an Arch Linux install, I chose the x686 install rather than the x86_64 because I wasn't sure what codec support would be like, and, I doubt I'll ever have more than 2GB RAM in.
/boot 100MB
/swap 2000MB (usually more than I'd configure, but, the system is a bit short on RAM
/ 10GB
/var/media rest ~210GB
I did a basic xorg install then added xbmc straight on-top instead of the window manager, I also installed the Nvidia binary drivers although I'm not really sure if this is needed (my experience is really with servers, not desktops).
I did a quick fiddle with the resolutions and 720p is a standard res, so I opted for it.
I then installed some additional packages;
smbclient, for streaming from my timecapsule
hellanzb (not sure what this is for :

)
lighttpd hellaworld (again, less said)
I threw a couple of files at it to test, but, without sound it's not really a good test; a DVD ISO, this played fine from local and streamed, an XVID file from the timecapsule, this played in FFWD, not sure why. I also tried a 720p x264 in MKV, this all seemed to play fine as well.
Once I can find a suitable soundcard with digital-optical out, and, a case with suitable WAF, I'll see what it looks like connected to the TV.
Thanks for everyones help
Andrew