Originally Posted by MOrlando
I was wondering if it were the power supply too. It just doesn't make sense, why put a factory sub (which I want to remove anyway) and not supply it enough power.
What's the best/most cost efficient approach to adding more power to the the speakers?
it depends, because like most things, you get what you pay for. you can start with a head unit with more power (probably something like 20w/channel), but it likely won't be as powerful or as clean as a good aftermarket amplifier that can push 50 or 100 watts per channel.
if it were me, i'd look for an amp. go with a high signal to noise ratio (above 90db). you can choose a 4 channel amp, which will power the front and rear speakers only, or get a 5 channel amp which will also drive a sub. better amps which have cleaner power will cost more. don't think you are going to get good sound from an amp claiming to make 500 watts per channel for $60 either.
when comparing power output of amplifiers, make sure you are looking at "rms" power, and not "peak" power, as measured in watts. there is a big difference. the rms power is what you want to compare and is the true measure of the amp rating.