$500 HTPC

Approximate Purchase Date: within 2 weeks

Budget Range: $500 ~ $550

System Usage from Most to Least Important: 3D/B-Ray/HD/Youtube videos, music, light gaming

Parts Not Required: Monitor ( I plan to connect it to my projector), OS (this budget does not include OS, that i can get anywhere, same price), speakers

Preferred Website(s) for Parts: Any (normally i use newegg.ca, ncix.ca, tigerdirect.ca)

Country of Origin: Canada

Parts Preferences: by brand or type: None, best and most reliable

Overclocking: Don't have to

SLI or Crossfire: doesn't have to

Monitor Resolution: 1920x1080

Other parts needed: Wireless keyboard with built in mouse.

Additional Comments: I'm new to HTPC and its abilities, so i apologize in advance for stupid questions. I'm building a little entertainment area in the basement, I'm getting a Sony 5.1 home theater system (HTSS380). I will be using the HTPC to watch blue ray movies, and even 3d movies (is there anything special required for computer to output 3d movies besides a graphics card that supports HDMI 1.4a?), YouTube etc. and light gaming like CoD black ops.
From all the experienced HTPC users out there, if you can recommend somethings and tips on how to get more out of it, or setup, it will be greatly appreciated.

Thank you in advance!