well for $10 you could just get some normal speakers that would work just as well as the 20 or 30's would...
I have found that with speakers... if you just need a set, then get some crappy $10 ones... because that is what they will be... just a set. however... if you want some SPEAKERS, you gotta spend a littly money.
try and search www.newegg.com
for speakers and set the min price for 8.00 and the max price for 40.00 and see what comes up that interests you.