I have an
AVERMEDIA AVCPCIH727 Hybrid Capture HD Card.
Only supports up to 1080i/720p but is also half the price of that Hauppauge and doesn't take up desk space since it's an internal card.
Both devices however are unable to record from a PS3 through HDMI because Sony though HDCP was a good idea but they will work fine if you use component cable inputs.
Processing power shouldn't be a worry really as you're not really gonna be using the PC while recording, as for editing, all you're really doing is splitting the footage and adding an into/outro if that's your thing, it's just the rendering/upload times and bitrate that are the main concern if you want it to look even half decent on Youtube.
I'll get round to my own Let's Plays eventually.