This value is measured in Ohms. It doesn't determine high or low quality but you should choose amplifier and speakers that are close in impedance rating. Speaker's sensitivity tells you how loud the speaker is per 2.83 Volts input. The higher the sensitivity, the weaker the amplifier you'll need to drive them. This is the ratio of speaker's volume to the underlying static of electronic circuit.
Higher ratio is better because it provides cleaner sound with less noise.
The room in which you put your speakers can have a very big effect on the sound quality. Reflective surfaces like windows or hard floor decrease the quality of sound. The best listening space is between two main speakers. Moving a speaker, especially the subwoofer, can make a large difference. Click here first for a popup window with the code to enter before checkout.