For those of you using the 5.25" speakers:

how does it sound? I can only imagine that it wouldn't sound as good as the speaker box that MSA sells because they're parallel to each other and are behind the seats? Sorry, I'm not too keen on the sound system business :[

FAIW, you can run the output from the stock radio to a power amp hidden below a seat, if you're not content with 3.5 W but want the factory look. I also really like the look of Mike's rear panel. Put all of this together, and you'll have OK sound -- but sound that you can actually hear. Note that much of that 10% THD will disappear when the radio unit isn't driving as much load.