i like my stock head unit in my truck but i want to get an amp and a 12" sub for my truck. i talked to a few different places and i get a different answer every time. i already have a stock 6 cd changer so if i get a new hu i'll need to spend more for a aftermarket one. my question is will it sound that much better with a new hu. does tech12 make a box for just one 12" that fits under the single seat in the back. also whats is a good amp sub combo for a good price.