The RMS rating has nothing to do with volume output. The sensitivity and power compression do. The RMS rating has more to do with mechanical/heat failure. The price of the speaker also has nothing to do with volume output.
If he never wants to buy more power and doesn't want to sacrifice SPL then listening to speakers with a higher sensitivity would be the way to go. He would also want to look at making the vehicle quieter.
Doubling the amount of power will only net you 3 db's, unless you start running into power compression, then you'll get even less from it. It takes 10 db's for it to sound twice as loud as before. So going from 22-25 watts to 100 will only get him about 6-7 db's and a little more dynamics.
It still sounds like his bet is to just follow his current plan.
I have 2 IDMax 12's in my Mustang. The RMS rating on them is 1000 watts each, people regularly put 2000 to them. I have them in a 2.5 Cu.Ft. sealed box. With
only 50 watts each they are loud enough to make my car rattle and hear it in my house. If the RMS power rating was any indicator I would barely be able to hear them in my car.
For awhile I powered them off the rear channels of a Pioneer deck(DEH-P4000 there is a LPF for this in the deck) at 20 watts each they were loud enough to over come the road noise in my car with NO interior, an exhaust that ended right under the firewall and the windows down at highway speeds. Again, the RMS rating has nothing to do with overall output.
I've also had them at 1200 watts (600 each) and it was far louder than anything I'll ever need.
PS, The only reason I'm throwing this out is because I've seen many people who were convinced that they NEEDED this or that for good sound. After getting them exactly what they were asking for they were disappointed and only then were they willing to listen to what we were saying. Telling someone they need a bunch of power or expensive speakers when they just want a small improvement is like telling your grandma she needs a Mac Pro to check her Email.
yes, anything over stock is generally going to sound better. When you compare paper cones to actual composite materials, the difference is quite clear.
however, be mindful of the RMS wattage of your new speakers.
all speakers have a perfect range of wattage, where they are the most efficient in their ability to reproduce sound with little distortion.
more expensive speakers typically require more watts. and if you cant throw enough watts at them to make em happy, you might as well stay with stock speakers.
if you arent using an external amp, and are using the radio's internal one, make sure you know its RMS rating and try to match the speakers to it.
then again, you can take 100watt RMS speakers and hook them up to a 22watt RMS headunit and still get kick ass sound, but its just not gonna be the best your speakers can do.
