For less than $100, the Logitech
z-2300's are hard to bet. They provide a much fuller sound than the over-hyper (IMO) HK SoundSticks.
I listen to everything from classical to prog and jazz and these perform very nicely.
The Logitech X-230's mentioned are OK, but they distort and don't really have a lot of presence.
If you want something to match your Mac a little more, Logitech's
Z-4i's are pretty good for less than $70.
I have both of these speakers and am quite pleased. Now when I get those Klipsch
ProMedia's...