If you are willing to give up some trunk and cut your carpet, or replace it, you can rig a basslink in the spare tire well. Sounds decent. Still the problem of mid-lows in the cab, but I'm not sure you can solve that with a big sub anyway. The best solutions seem to be a custom box in place of the cubbies.
WRT to the stripe, if you are hooked up stripe=negative to the speaker and wired stripe=positive to a Japanese head unit you'll be out of phase. The german's wire opposite to the Japanese. I found this in 2 cabs. When I reversed the polarity at the head unit (because I was replacing the head and it was easier to get to those wires at that time), the sound improved dramatically, even with 17-year old stock paper cones. Mind you it was not Carnegie Hall, but was the difference between something that was usable and something that I just turned off.
