Had it done by a local shop. It is two pieces of plywood + carpet

 

I have an Eclipse 40x2 amp behind the seat. It's pretty flat and doesn't compromise legroom. I wanted a factory look, so the amp takes line-level input from the factory headunit. For speakers, I got Boston Acoustics 2 piece component systems. They come with bridge, so it's like a coaxial speaker, but there are crossovers mounted in each door. I went to Al and Ed's. They screwed it up 3 times (trouble with the left channel) but I finally made them replace everygthing, and now the sound is much better than OE. Less bass than the crappy factory speakers, though, and it will distort if I crank the base on the headunit at high volumes. All in all, though, I'm pretty happy. It cost $1000, but half of that was the speakers.
Bduel