I bought a used Acura TL back in November of 2004 when the head gasket gave out on my 12 year old Acura Legend (for the second time… had already footed an insane bill once to repair the same thing). I immediately took apart the dash, put in an adapter that converted the CD changer input to a couple of RCA audio jacks which I then ran through the dash into a little cubby/storage slot. After adding a gooseneck PDA holder, I had an iPod-ready car.
For my birthday in January of 2005, I got a set of Polk Audio DB6500s on the cheap off eBay and installed them myself. This involved taking the doors apart, cutting out portions of the doors, and yes, sticking a knife in my leg. For the next year I had fantastic audio in the car minus any bass whatsoever. The car had come with a subwoofer, but it was horrific, so I disconnected it. Great music sans bass. Until my next birthday.
For my birthday in January of 2006, I got an Infinity Basslink, a self-contained small profile 10-inch subwoofer and amp combo thingy (again, courtesy the fine folks at eBay). This time I had Best Buy do the install, and they did a great job. Since then I’ve been enjoying a wonderful audio “experience” as I motor around town. The subwoofer takes up very little room in the trunk and provides a terrific sound, though it is designed more for quality rather than quantity. I can’t entertain neighboring cars with heavy beats.
I really do recommend the approach of putting a solid pair of tweeters and mids up front coupled with a subwoofer. I mostly fade out the back speakers so they are inaudible in the front seats and just provide a bit more sound in the rear seats. You end up with a great shape to the music and by putting all the sound in front it maximizes the illusion of the bass originating from up front as well.