@linuxgod The Focals (Toyota Integration series) I recommended are a bit more expensive than the solution @bamm'recommended. But on the plus side, the ones I recommended looks stock and comes with clips and adapters to plug into the factory terminated plugs, so you don't need to do any mods to get them in the vehicle.
To be completely honest, if i had to do it all over again, I would only replace the tweeters in the A pillars and the tweeter/mid in the center and the mids in the two corners of the dash. The stock woofers in the doors do a great job with bass with the stock headunit/amp. The Focal woofers are fantastic, but without a proper amp, i doubt you will hear the $$$ as an upgrade. One of my mates have amped his system (Identical setup to mine, but have amped the woofers in the doors) and they now sound well worth the $$$ value in upgrade. Before amping the woofers, they were only identical if not marginally better than the stock woofers.
As for aftermarket speakers sounding a bit lower in volume, that is not my experience. overall, for pink noise played at level 20 was 1db louder in my rig and I haven't used an external amp. The Focal gear I got were of slightly higher impedance than the stock woofers but I cant really tell the difference. The Polk audio 3.5" two way coaxials I used to replace all three units in the dash are also of slightly higher impedance, but they are a lot more efficient than the factory units, so it sounds louder and much crisper.