Speakers for under $100?

[HeXploiT]

Are there any decent speakers out there for under $100 that can blow away my Altec Lansing 251 set? I've been looking at some refurbished Logitech Z-5300's. Are these any good?
Any suggestions for a decent cheap speaker set?

 

[fierydemise]

Logitech z-640s great value but a bit harder to find

 

[HeXploiT]

I was actually looking at some of those but i wasn't sure if they would actually be a step up from my Lansing 251 set. Lots of these X-530 unit on the market as well.