Avoid USB capture card as long as possible, because they aren't usually very good and could lead to some errors/delays/frame drops etc. during capture; the same for USB audio card...

Take a look at my threads:

http://originaltrilogy.com/forum/topic.cfm/High-End-video-capture-cards/topic/15115/

http://originaltrilogy.com/forum/topic.cfm/High-End-audio-capture-cards/topic/15214/

just to have an idea which ones are the best; of course, you could still obtain very good results using other cards, but if you are lucky, you could grab one of the high-end video capture card for less than 100US$, and audio card for about 50US$ - very well invested money IMHO!

After you have bought both card, start a thread about audio and video capture technique, I'll be happy to help you then.