I went for the nav system on my 2012 Ltd. so it has the same crummy sound system. I've been looking at options starting with replacing the speakers. The ones I want to use are listed as not fitting by Crutchfield, so I decided to pull out the stock 6.5" drivers and take a look. I was DISGUSTED by what I found. The speakers in my $31,000 car are worth about 3 bucks each. The plastic mounting bracket is also the speaker frame, the cone is cheap paper, the suspension treated cloth, and the magnet is so tiny it barely deflects a compass held nearby. I expected better from Toyota.
The good news is that the Polk MM6501's will fit easily. Once the existing unit is removed, there is a 6.125" diameter hole in the metal with almost 5" of mounting depth clearance. Pretty much any 6-1/2" speaker will fit.
The existing speakers have a foam ring around them that mates with the edge of the 6" diameter plastic port in the door panel. There is then an inch of empty 6" tube behind the grills in the door panel.
The MM6501's are rated at 94dB sensitivity which is about 6dB better than what I expect from the stock units. That will mean effectively the same thing as having 4X as much amplifier power. It remains to be seen how they will handle the stock EQ. One bridge to cross at a time....
2012 V6 4WD Ltd.
if you're not part of the solution, you're part of the precipitate.