That's the spirit! Love those HHR's now start saving up!

 

One thing you may want to check is the balance and fade settings on the radio.
As long as all the speakers are working, you could have one of these settings out of adjustment and in turn limiting the speaker output.

I know with mine, if I fade it to the back the volume is only half as loud in the front seat area. I generally keep mine faded a little more to the front to keep the volume up.
The front speakers seem to have much more ouput than the rear door ones.

 

Oooooh, good idea. I'll check that out tomorrow. 8-)

 

Amplifier and speakers.

A lot of people put new speakers in their HHR's without put an amp in first, which is backwards.

First, put an amplifier in to power the stock mids and tweets. They will be much louder and cleaner.

I've done this on 2 vehicles and every time they are amazed at how much better the stock crap is and how much money they saved by not replacing all the speakers.