Need an excuse for a 40″ computer monitor (or a PC in the living room?)

Well, you’ll still have to come up with that yourself, but as for how to build a HTPC from scratch for under $1000 (with some tweaks in the article to get it under $500 or well over $1000), you can take a look at this article over on Engadget.  From all I’ve read (in this article and others) ensure that your video card can hand HDCP (High-Def Content Protection, I believe),  otherwise you’re going to have some issues getting that high-def content out to your display.