Do you want just two speakers for stereo (2.0), stereo plus a subwoofer (2.1), or 5.1, 7.1?
I just want 2.0 and I've had the Klipsch ProMedia Ultra 2.0 and the Creative GigaWorks T20. The Klipsch sounded good but I had problems with the internal amp cutting off. The GigaWorks have had no problems since I've owned them. Both of these speaker systems are under $100.