Aftermarket Sub

Just bought an 04 TL with navigation! Love it so far but no bass?!

I've got a sub/amp from my old Acura RSX-S that I want to install in this one.. Am I better off tapping the signal for bass before or after the factory amp? If one way is better than the other, can someone explain the process of wiring the LOC if required..

Thanks, and I hope this forum serves me well!