Well, I just finished installing a sub & amp in my work truck. I spend all day long on the road, and the stock GM stereo in my '07 2500HD leaves a lot to be desired on the low end. Mids & highs seem quite nice, thanks to GM's standard component speaker setup in the doors.

I installed my Zapco AG350 amp & JL 10w1-4 subwoofer in the back. Unfortunately, I did not want to spend over $100.00 on a proper line out adapter for the stock headunit, so I bought a line out converter. It seems to work well.

The sub evened the sound out quite nicely, and now I can cruise the service truck in style... The guys at the shop are all jealous...