HTPC & Gaming Crossfire or Not?

Hello... newbie to forum.

I was thinking of trying to crossfire an All-In-Wonder type card with a HD 5770.. doable or not? worth it~?~

Would like to have gaming capability for newest games and video capture/playback in the same box... a combined HTPC / gaming machine (DirectX 11)~?~

Currently owned equipment: Sony KDL-52Z5100 (TV) and Sony STR-DN100 (AV Receiver).
The AV receiver is my HDMI combining unit with HDMI to TV.

PC functional goals: Internet videos, Hulu, convert VHS and HI-8 tape, burn DVD, play Blu-ray and DVD, gaming and typical "home" PC needs (still pictures, MS Office, etc.). -- I do not plan to store movies on the box, but like the idea of Tivo type capability for local broadcasts.

HTPC thoughts thus far:
Case - Silverstone LC17B
PSU - Corsair CMPSU-750HX
MoBo - Asus P6x58D-E
CPU - Core i7-920
GPU - Sapphire HD5770 Vapor-X
RAM - Corsair XMS3 6GB (3x20 PC3-10666)
HDD - WD 1TB WD1001FALS (SATA II, 7200)
BD/DVD - LG GH22LS50 (no real desire to burn BD)
Flash - Silverstone FP35B (memory reader, 3.5")
CPU cooler - Corsair Hydro H50
Key/Mouse - IOGear GKM561R (wireless keyboard w/trackball)

I'll take suggestions on all, but looking for ideas on how best to do video/audio capture (inputs) and keep it clean and where possible minimize duplicate software.

Thanks in advance.