with aftermarket stereos the harness is made to simply match up colors. the reason the bass doesnt sound good is probably because the bass is too high on the deck or the speakers are just crap. i installed my old pioneer in my boy's galant and when we turned it up the bass sounded like ass, but thats because the speakers are still the crappy stock ones. so check the output levels on your stereo or get new speakers. stock speakers were never meant to sound good with aftermarket stereos.