So I just parked my '03 TL-S with a bad tranny and began driving my replacement vehicle ' 03CL-S 6sp. I could not help but noticing that the stereo in the CL-S is either faulty or is horrible in comparison to the TL-S. It is weak and I can barely hear it with windows down even at low speeds ??? Thanks!!

 

Speakers might be blown, or dry rotted. First step I'd take would be to disassemble the doors and inspect them visually.

 

The TL has a factory sub whereas the CL does not, making it significantly louder. However your speakers could be toast or the factory amp may as well be toast. If you drop in really any speaker thats about $100 and up it will make a huge difference in sound, if its still not loud enough for you then you may want to think about getting a new head unit and speaker amp