My wifes 07 HHR has the premium sound system, and I have an 06 with the CD Mp3 player. Maybe just my old ears but the regular sound system sounds better than the premium one. I was wondering if the door speakers are the same on both systems, or if the premium system uses door speakers that don't produce as much bass so the sub sounds better?

 

They are different speakers in premium system vs. regular system. They still are the paper cone oem style though.