I've seen a number of DVB cards on eBay lately for about $50 shipped. Some of the auctions claim that the cards will receive HD channels. One specific model is a Twinhan VisionPlus VP-1020A. My PC is hooked up to a 42" 1080p monitor and PBS HD would certainly look nice on it. Though I wouldn't bother with the card if it wouldn't do HD.
Would also need to be Linux capable.
Welcoming all opinions.
I may be able to help you some with the Linux part. I'm pretty sure that card is supported, but I have not used it. My card is a Kworld DVB S-100, with a Conexant CX88 chipset.
DVB support is in the kernel. You will need to enable v4l2, dvb, i2c, and support for your particular chipset. There is no external driver to install. You will need a viewer program, such as mplayer or kaffeine. You will also need a way to move the dish, kaffeine can do this, or a standalone program like xdipo.
A decent DVB card can certainly tune in PBS-HD (my favorite channel), but whether it is watchable depends on many things. You need a good video card (at least Nvidia 6200 or comparable), and a fast cpu ( I have 3ghz and it's not overkill). There have been recent big performance improvements in xorg-server, 1.4 runs WAY faster than 1.3. I have a widescreen monitor and watch tv directly on it, but a good video card should be able to drive a high-def tv like yours.
Good luck and happy viewing!