Help buying ipod speakers?

i need to buy some ipod speakers and i've seen some that im interested in in argos.i dont want to spend too much.about 40-60 quid. but the problem is i dont understand what speaker watts means.in the catologue it says the higher the number the better the sound quality will be.but then theres some in the catlogoue worth about 100 quid and their speaker watts are lower than the ones im interested in which are about �40.so im a bit confused..