I'll just give these basic points on 2.1 speakers.
1) Desktop speakers don't normally go below around 45Hz, so to get a full range sound you should use a sub-woofer
2) The aim of the sub-woofer is to complement the main speakers, you want the sub-woofer to be invisible, meaning the sound appears to be only from the satellite speakers, yet when the sub-woofer is disabled you notice the reduction in quality.
3) Most 2.1 systems are optimised for games and films and not for music.
4) The satellite speakers included in almost all 2.1 speaker sets the drivers are to small, meaning the mid range frequencies are poor.
5) The best setup is desktop speakers with 4" to 5" drivers for good mid range, then adding a sub.
I'm using an Edifier S530 2.1, however I changed the included satellite speakers to some Yamaha Pianocraft speakers that gave a far better sound, particularly better vocals and mid range. The amplifier in the S530 is not as good as my Pioneer separate amps, however it's still sufficient to cleanly drive the Yamaha Pianocrafts.