I've got a 09 Nissan Sentra with the factory door speakers. I recently put in a JVC KD-HDR70 cd player (puts out 20watts) and obviously my speakers sound better now than with my factory HU. Think it would be worth changing out the speakers to some decent aftermarket speakers? I've only changed them when I've had them running off a seperate amp (60watts plus), but how much better, if any, would they sound over factory considering the power they would be getting? I don't have a certain brand in mind, I was just curious.