Capture Card

[Tohk]

New to the scene.
I'm finding that I can spend anywhere from $20, to $800 for a capture card and I'm not sure what's required. Can anybody lend a hand? What's the difference in performance in a cheaper or more expensive card?

Also, I saw the thread on the CRT's. Does this matter whatsoever for anything other than aspect ratio? because I can 4:3 my LCD.

[GothicLogic]

GV-USB2 (I recommend) or Dazzle DVC 100.

CRT for response times, lower ms the better