Just finished installing 4 Polk speakers in my 99 Corolla. I've read a few horror stories but this was a piece of cake and only took 4 hours. Could do it again in half the time. Installed 2 way db650 6 1/2" in the front doors and db675 6 3/4" in the rear deck. When removing the window control panel, make sure you use a small screw driver and pry up the front edge first and then slide forward. All the hardware removal is explained in the Haynes manual.
The door speaker brackets are pop riveted in and you have to drill out 3 rivets using a 3/16" drill bit, being careful not to enlarge the holes. You'll be using the same rivet holes to mount the new brackets with #14 screws. Toyota uses a plastic water shield behind the speakers and I reused them. You'll need to use the Haynes manual wiring schematic to identify the correct plus and minus speaker wires which I used the same wires and soldered them onto the new speakers. You don't need to unhook the door handle and it can be manuvered through the door panel hole. Only tools you'll need is a small screw driver, #2 phillips screw driver and a regular screw driver. After removing the window control panel, pry up the arm rest cover straight up which has 4 tabs holding it. Then you'll find 2 phillips screws to remove. There's a plastic pop rivet you'll need to remove which has a phillips center pin that you take out so you can reuse the rivet. Remove the knob and black cover for the side view mirrors. By using a straight blade screw driver, just go all around the outside of the panel and pop it loose. Lift up over the door lock and you're in business. Be careful to peel back the clear plastic and you can reseal it in place. The 6 1/2" Polk's were shallow enough to not get in the way of the window glass. I used Metra speaker adaptors to replace the factory adaptor, $8 on eBay.
To install the rears, you have to lower the back seat backs, pop the 3rd brake light assembly out and unplug it. Pry the front side of the brake light first and slide it forward. There's 2 plastic pop rivets holding the whole rear panel in place and the heads broke off because of UV damage. Slip the seat belts out of the slots and lift the whole panel up and forward. The stock rear speakers are mounted on a special spacer adaptor ring and held in place with one small bolt. The 6 3/4" Polks fit perfectly in the stock plastic adaptors. Since the basket of the new speakers are larger than the stock ones, I used tin snips and cut 1/2" slits every 1/2" or so and bent the tabs I created inside the round opening of the sheet metal. The metal is thin and was easy to cut and bend using regular pliers. The new speakers with the higher mounted tweeter dome fit perfectly, nothing touching.
Buttoned everything back up and tested it out using a Pioneer DEH-P2600 head unit, which has a 50x4 amp, 22 RMS watts. The Polks can handle 60 RMS watts. I'm a 52 year old classic rocker that's not into thumping rap, just clean loud high fidelity. No need for a amp or sub. These Polks crank out plenty of mid bass with crisp highs. These speakers out perform the Infinity Kappa's I have in my Jeep. Same head unit but 5 1/4" 2 ways up front with 6 1/2" 3 ways in the rear. I have a Kenwood powered sub under the seat but really isn't required in the Corolla for my music tastes. The Kappa's cost 3 times as much and requires lots of volume to get them to sound good. Not the case with the Polks. Picked them up for $49 per pair on eBay! Head unit was only $89. A $200 complete system that sounds as good as something that costs 5 times the amount. The money I save goes towards expensive gasoline! You can spend more than that just buying a pair of funky speakers at Circuit City.