Being that I'm an installer, I've tired some things like the capacitor trick. I found that I didn't like it, I don't know what some people are hearing. After I put the capacitors on the front speakers, I realized just how bad the factory subs sound and the overall bass output was far less. The front speakers actually are very good and don't distort as bad as the subs do. So I removed the caps for the time being, until...

I knew I was going to add a aftermarket amp because I just wasn't satisfied with the not so clean and not so powerful factory amp.
So, I changed the head unit for my Pioneer and added my JL Audio 500/5 five channel amp which is 100x2 for the front, 25x2 for the rear, and 250x1 for a sub. I removed the door panels to run my wires to the speakers, and realized how nice the front speakers actually are. They are NOT your typical factory speakers, like the old Chrysler/Infinity speakers. These speakers are true Infinity speakers with Polypropylene cones, rubber surrounds and a huge magnet. The tweeters are a nice dome style unit that is actually positioned good, pointing up towards the rear view mirror which I didn't know before.
So...I just amplified the stock front speakers with clean 100x2 power with the amps crossover set at about 63hz and they sound great!
The stock front speakers produce alot more, cleaner bass then the stock subs do. I left the stock subs hooked up to the factory amp, on the rear outputs of the head unit, that way I can use the fader to shut them off if I want to.
I love the sound Im getting from the stock door speakers now, very loud, clear and lots of mid bass that you can feel on your legs!
The rear 25x2 outputs of my JL amp are not being used for the time being, some day I may use it for the stock subs for some fill, because...
I added a JL audio 8W7 8" sub in a sealed box using the 250x1 from the amp for some real bass that moves the hair on my head if I want it to!