The final specs of my machine are as below;

• AMD Athlon 64 - the 2800+ in particular. I tried to keep the "spec" down a little here in a hope that this would also keep the heat and the fan noise down a little.
• 1GB PC3200 RAM.
• 200GB Seagate Barracuda IDE Hard-drive (7200 rpm) - I went IDE for this as there seem to be some "complexities" around getting one of these motherboards from Shuttle to install a clean copy of Windows from a SATA drive and I didn't want the hassle.
• ASUS V9520/GeForce FX 5200. I went for this because it doesn't have a fan strapped on it adding to the noise. I figured (from reading around a lot) that it was sufficient to do the job for Media Center and, so far, it seems fine.
• NEC ND-3500A Dual Layer DVD/RW (an OEM'd version of it)
• NVidia DVD Decoder - you'll need a decoder if you want to play DVDs as, just like Windows XP, you don't get one thrown in.
• Hauppauge WinTV-PVR-500MCE dual-tuner analogue TV card for Media Center.

And that's it. The trickiest thing was waiting for the Hauppauge card to come out in the UK. In the end I ordered this (PAL version) through the US web site and they ship them out of Ireland to European customers.

The Hauppauge card works great and I can confirm that it does fit into the Shuttle case but it was touch-and-go for a little while. I'm slightly worried about how hot it might get in there!

Beyond that, I'm very happy with the picture quality (I'm using a regular TV set here) and I like the dual-tuner functionality. I'm particularly impressed with how Media Center 2005 handles TV, it seems to work exactly as I was hoping it would although I'd still like to be able to get what I'd call "picture-in-picture" if that's possible. The radio capabilities also work pretty well but it's clear that Media Center could have extra functionality around radio that it doesn't right now (i.e. a nice channel selection page and a record facility but you can't have everything).

I spent a little bit of time thinking that the Hauppauge card didn't work before I realised that the automatic channel selection has selected around 14 TV channels for my area and I needed to go and refine which ones I actually wanted to look at as most weren't properly tuned. With that sorted, everything works fine.

So,  all-in-all a very good experience.