Advice for a $600-800 HTPC build

My current pc is on its last bytes, and I've been looking at building a new one this time (currently using laptop). Was originally looking at a desktop rig, but have since realized I'd prefer an HTPC set up. Done a little searching around, but haven't quite found the right combination.

APPROXIMATE PURCHASE DATE: next 1-2 weeks

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: watching (lots of) HD video files (.mkv, .mp4, .avi, etc.), watching / recording TV, streaming (Hulu / Netflix), music playback, possibly light gaming, preferably at 1080p (starcraft II, dragon age), general use

PARTS NOT REQUIRED: monitor (plan to use my current 50" 1080p plasma - any issues with a plasma monitor for an htpc?)

PREFERRED WEBSITE(S) FOR PARTS: newegg.com, amazon.com

PARTS PREFERENCES: no brand preference; would prefer a smaller media-center sized case, but not required

OVERCLOCKING: Yes / No / Maybe SLI OR CROSSFIRE: possibly

MONITOR RESOLUTION: 1920x1080

ADDITIONAL COMMENTS: system would need wireless card / adapter