I third the mounting ring. I had the pioneers you last mentioned and they are decent. I replaced those with some JVC's I picked up at Best Buy and they rock! I usually crank my music up too and so far they've held up. What ever you do, go to Best Buy or any local store you can test speakers at and LISTEN TO THEM. Also keep in mind the store likes to tune the head unit hooked to the speakers to make them get the best sound (which is fine if you know how to set it as they did). You also have to take in consideration that the speakers are on the floor, not by your ears like in the stores. Crutchfield is a great place to order from. Excellent customer service! My dad bought his system from there and their support helped him when he ran into wiring problems. (On the phone and emailed him schematics and worded instructions ect.)
The Polk Audio's kg6mov recommended rocked on display but were too much for my budget. These are the ones I bought:
Sound great for the money. I recommend to go to a store and TEST the speaker before you buy them. Take a 3.5mm to 3.5mm cord or iPod USB cord and go to best buy plug it in to the head units and test test test!!!
My system: JVC Head unit, stock Infinity amp, two JVC (fronts), 6.5" subwoofer back left door (powered off of stock amp), 8" 150W sub (on floor behind passengers seat), NO SPEAKER IN RIGHT BACK DOOR. Good enough to to share my music with everyone at a red light