I've been trying to find the best way to upgrade the stereo in my "new" FZJ-80. I had to replace the rotted out foam surrounds in the front door speakers. That helped but it still did'nt sound great. The rear woofer wasn't working. There is a bass amplifier behind the right rear quarter panel that was the problem. Unable to fix it, I purchased a Rockford Fosgate 350S 2 channel amp (87 watts rms/channel) and mounted it on the bass amp bracket in the back. All the required inputs from the head unit are right there at the bass amp plug, except B+, which required me to run an 8 AWG fused wire from the battery. Just to see what it would sound like, I hooked up my home stereo Epicure M201's. These speakers each have 2 8" bass/midrange and 2 dome tweeters and each weigh at least 50 lbs. My wife said I was crazy. Laying down, they took up most of the floor space in the back with the back seats folded up. Anyway, the resultant sound was phenomenal. Clear, deep bass and powerful mid/highs. You can turn it all the way up (it hurts!) and there is zero distortion. I guess my point is that there is nothing wrong with the sound signal quality coming from the factory head. The problem is its lack of power and the small size of the factory speakers. My next step is to figure out a way to install some speakers worthy of this amp and still have room left for cargo.