couple of questions for all the wagon owners out there. I have a stock stero in my wagon with 4 speakers in the doors. The back two aren't working and with the front two speakers carrying the load, the sound is pretty tinny and heavy on the high end. So my questions are:

1) what's the most likely reason why the back speakers aren't working?

and

2) what kind of speaker/amp set up would you recommend?

I want to keep the stock radio receiver/tape deck as I listen exclusively to the 1,000s of MP3s I keep stored on my portable player which uses a cassette adapter.

Thanks for the advice-

Nick Zaharias
1990 240 Wagon
93,000 miles
Bilsteins & IPD Sway bars