Adding bass to stock system

I debated putting this in the Car Audio section but since it contained vehicle specific questions I decided it belonged here.

First off, I own a 1997 Park Avenue Ultra and I am very satsified with the stock sound system. I just wish it had a little more bass. I was thinking i could tap into the wires going into the amp in the trunk and use some line out converters. My only concern is that the stock head unit may be cutting out the bottom end frequencies to protect the stock speakers and if i install subwoofers it will end up sounding like shit.

So, is this the case? and if it is; will installing a new headunit be pratically possible with the ultra's premium sound system?

Thanks in advance for reading
Brad

Interesting thoughts you have there.. iirc the Park Ave's concert sound System did not use a Gain amp of any sort... It was all head unit.. But GM didn't use the greatest speakers.. You may consider replacing the rear speakers as they are not as good as they could be..