Shuttle sells a purpose-built HTPC with HDMI out, a blu-ray drive, and an integrated 7" touch screen on the case to control the system. Lil' pricey, but it sounds like it does pretty much everything you want it to do:
Shuttle XPC | PC Made Modern
If you want a slightly less expensive option, check out Sager laptops ( sagernotebook.com ). They're coming with HDMI ports now, and you can get one for around $850. The last time I checked you could upgrade to a blu-ray drive for something like $150, so you'd still be about 300 less than the Shuttle.