I agree - your budget seems a bit restrictive (as in it will 'restrict' you to what's on the shelf at wal-mart).
The real magic in the 2.1 category doesn't begin to happen until you go above $100. At that point, you can get into a set of Altec Lansing's FX4021 speakers. While they tend to have some trouble at the loudest volumes (typical of small speakers), they feature a very 'clean', 'deep'-sounding subwoofer that uses a pair of 5.25" woofers in an "isobaric" clamshell configuration that doubles the force that can be applied to the piston area, making very deep bass possible from the little cube.
At the $150 mark, I've been very happy with my Cambridge Soundworks "Microworks II" 2.1 set. It goes beyond most PC speaker sets to provide a very 'hi-fi' sound, more characteristic of a home stereo than a set of PC speakers.