I have the Logitech Z-560 4.1 system and am quite pleased with it.
If you are concerned about bass response, the 560's have a big sub (my printer sits on it) with plenty of power (188 watts of the system's total 400 watt RMS power).
I use the speaker system's own "M3D" processing to drive the rear speakers, and that works pretty well, putting sounds with reverb on the rears. Too bad Apple has no 4-channel sound.
The control panel unit is great, with a nice blue ring...