I am restoring my 1988 Silverado. It is a long bed standard cab. I installed a new Sony radio and CD player in the center of the dash where the old casette used to reside. I replaced the front speakers with high grade units, but the rears are still awful. I would like to add a lot of bass response as well as some good mids and highs. Has anyone had success with such a project, and what did you use???