Similarly to Dan, I wouldn't buy anything cheaper anyhow.
There are heaps of external capture cards on eBay from the Hong Kong. The average around $10 with $10 postage.... However these are USB, please DO NOT BUY ONE FOR MAC! As already stated, USB is the worst idea for video capture on a Mac.
I'm looking at a canopus myself at the moment, but wonder...
Has anyone used it for playing console games, live?
I don't mean recording, because I know that is already possible? I'm more so asking for actual experience with fps and audio quality if anyone has used it... not just stats on the net