tbh if ur spending <£30 on speakers there really won't be much difference between them. i would personally save up for a while to at least get the z4s. if u get speakers for £20 then they would probably sound worse than ur current ones. i have logitech x-230s and they sound crap, as does my friend's £20 set of creatives. i personally don't see the point of buying a new set unless they are going to sound much better than my current ones. its just not a good return for investment otherwise