I'm looking to upgrade the sound system in my 2003 TL type S but I'd like to keep my factory head unit possible since I think the dash would look funny without it. I've put 3 JL 8W6's in the truck connected to an amp but it still doesn't sounds like I want it. Can I replace the remaining speakers without replacing the factory HU. I don't want to go crazy, I just want a good sounding system that allows be to control then subs. I'll be replacing my amp with one with sub controls soon. Any recommendations?