lol the creative xifi is way more than 30-50 (190 i think at cheapest) and the logitech z's r around 400. those r really sweet products but if ur budget is that low then try cyber-acoustics 2.1's which r about 30. i got them for my lower-end comp and they do the job just fine. and for the SC go for the creative 24-bit but if u have a good mobo then u might want to just think about using the onboard audio instead.
Chris