My poor 37 " HD television still hasn't had any HD content on it. I used that as the flimsy justification to replace my PVR with a new Home Theatre PC (HTPC) Myth TV box. It's probably going to cost about three times what a decent Humax FreeSat box would cost, but I like the flexibilty of setting up my own system, and having the extras like automatic advert detection. It should also be an interesting project!
The UK doesn't currently have HD broadcasts on terrestrial TV yet, and there are limited options for HD DVB-T tuners. I decided to get one DVB-S tuner for HD on FreeSat, and a twin DVB-T tuner for general viewing/recording on FreeView. As I live in a flat with a single satellite input, it would be difficult to use multiple DVB-S tuners (you need a separate input for each satellite tuner, as it needs to switch the signal orientation that the dish receiver listens on).
Apparently Channel 4 are planning to switch to a new satellite format (DVB-S2) at some point this year. This left me with just one choice for the tuner that I could find - the PCI Hauppauge WinTV-NOVA-HD-S2. For the DVB-T twin tuner, I went for the USB PCTV Diversity Stick Solo, mosly because it was the only twin DVB-T tuner capable of receiving HD terrestrial TV when it is finally broadcast - so I thought. Actually, it was mis-advertised by DABS (it doesn't support HD), but I stuck with it anyway as otherwise it was working well. For both of these cards, I checked the support under Linux first.
For the system itself, I started looking at an AS Rock NetTop, such as the Ion 330HT-DB. With the new Nvidia ION graphics card able to handle all of the video decoding for HD, it doesn't need a high-powered processor to support MythTV. Unfortunately, it doesn't have a spare PCI slot to host the Hauppauge DVB-S card. Even if I managed to find an HD-capable USB tuner I read some articles casting doubt on whether USB 2 was fast enough to support the volume of data needed for smooth HD.
I then came across the Shuttle SN78SH7, which is what I ended up buying. This is a bare-bones system intended for an HTPC system. It is small and quiet and doesn't look out of place under my TV. The motherboard has a built-in NVIDIA GeForce 8200, which like the ION can handle the HD video decoding, and has an HDMI output for direct connection to the TV. It also has 7.1 surround sound, and is an Energy Star 4 system (power consumption is a consideration for a system that will be on all of the time). It supports the latest AMD processors - I got an AMD Phenom II 940 X4, a quad-core 3.0 GHz processor. Although I don't really need all this processing power, the cost of the Shuttle, the CPU and the memory was still a lot lower than any comparable Intel-based system.
I'm pretty happy with the Shuttle - it was straightforward to setup, and is inaudible when there is any background noise. It has a clever set of heat pipes that channel the heat from the CPU directly to the case fan, which helps cut the noise. One unfortunate aspect of this arrangement is that the AMD warranty is invalid if you use anything other than the heatsink/fan supplied with the CPU.
I had originally intended to include a Blu-Ray drive as part of the system, until I discovered that Ubuntu cannot play Blu-Ray discs directly due to the DRM included in the format. The only option open to me is to hack the disks, something I could do from my laptop and copy to the MythTV box.
For the hard disk, I chose a Western Digital Caviar Green 1 TB disk, mostly because of the energy efficiency features. It was a decision I'd come to regret (more later)...
I also got a KeySonic Super-Mini wireless keyboard with a built-in trackpad. Both the keyboard and the trackpad worked straightaway with Ubuntu, including the two-finger scrolling feature (it is a multi-touch trackpad). The quality is reasonable and it is an ideal size for an HTPC, but there are a few problems. First, the range is very limited - I get about 2 metres in my house, and that only when the USB receiver is in a front-mounted slot (although I do have a wireless network and other wireless devices that may be causing some interference). Second, the keys don't always operate smoothly, which means that you have to be quite firm when typing. As the keyboard is so small, it's difficult to touch-type without looking at the keys. Finally, some extra keys (e.g. Page Up) are activated with a function key. Unfortunately, this button is to the left of the left-control key, and I am always accidentally hitting the function key instead of the control key - very annoying for example when trying to copy/paste with Ctrl-C and Ctrl-V. This was an expensive keyboard, so given these niggles I would have some reservations recommending it.