Thanks for the suggestions, I'll try to get back to you on this after work tonight.
I haven't checked wiring yet, just discovered this last night on a trip to the hospital...
Don't know about the bass blocker...
The head unit's bass is up (in an effort to hear the bass, and I kind of left it there), treble turned quite a bit down.
I'm thinking about getting a pair of aftermarket 12" subs anyway with a seperate amp.
But yeah, there's sound coming from those speakers, but in the words of the witness (I'm never in my rear seat, so I never really noticed/had an idea until I played with the head unit, because it all sounded so "forward"), it sounded "very lacking" and "tinny".
I asked to clarify, and "it was there, just tinny."
Which to me sounds like either a blown speaker or some nasty crossover problem.
But I could definitely be wrong.
Also I didn't check anything yet.
Update to come soon.
It's just that in my e36 318, the bass definitely came from the woofers in back. I hesitate for a second to believe that the 6 speaker 318i system is any better in malleability to the e36 m3 system.