I have a 12" JL in the trunk hooked up to a 450watt amp, it's pretty loud but it's not a permanent setup.

In terms of speakers I've been looking around and was wondering about putting mid-bass in place of my two rear speakers, getting nice sounding speakers for the front and replacing the 12" JL with two 10's.

I'm obviously still not 100% knowledgeable on everything there is to know about car stereo systems but I'm attempting to learn and was hoping somebody could tell me if this is an idea I should pursue.

My deck right now is a two year old kenwood, it's nice but it's not the best.

The higher up in the frequency range you go, the more that it is going to distract your ear to the back of the car. If your just looking for loud good sound from everywhere, that isn't a problem.

Also, make sure that you have an amp on all your speakers, or you'll probably end up blowing them again.

But thank you for your advice.