I wouldn't know about that... but if you have a decent/minimal garage+tool assortment. And a nearby Home Depot where you can purchase MDF Fiberboard. I'd highly suggest checking out SonicElectronix dot com. You'd probably be amazed at just how much of an improvement you could do yourself... and their prices on stuff are excellent!
The cheapest route for a substantial gain would be installing a 4 ch amplifier and powering the 2 front doors with the front channels.... and bridging the 2 rear channels and powering a subwoofer instead.
If you don't need mega volume... I highly... Highly... recommend picking up just a JL-Audio 6W3v3 4-Ohm 6-1/2" Subwoofer. The specs for a ported box for that thing is a tiny .25 cu. ft. and it slides easily under the rear seat... and it's only 150Watts RMS. You'd be surprised how many adjacent drivers you could piss-off with that little sucker if your windows are down! :grin:
And for a minimal setup like that you could easily also mount the 4 ch amp under the other rear seat.
And I have to say for a small setup... that JL Audio sub sounds amazing, simply amazing.
I've gone thru about 4-5 different redo's in my Trac so far, each time getting a little bigger and badder. But when I need room I can just grab that little sucker and swap the bigger one for it temporarily and it's still quite pleasing, even for someone who rides around with a 12" 600 Watt RMS setup most of the time. :banana: