I guess I read “Casual gamer” differently than you intended. I thought it meant, “I like new games, and would like to play them”. If you’re only going to play maybe 1-2 games per year 8600 is fine. If you want to play some higher end FPS games with nice framerates, it’s waste of money.
The Dr. is correct on the HDCP, though personally I dont consider a budget box to include and HDMI monitor, an HD-DVD player, or a Blu-Ray drive. So the HDCP point is correct, but perhaps not a factor.
The DX10 is useful for aeroglass on Vista, but you’re running XP, which doesnt care about DX10.