My stereo guy took on his first HHR and things worked out, but it was not without ripples. Since my ride didn't come with the premium system, GM gave us flack on the factory sub box, but it was eventually resolved. Replaced all 4 door speakers, but the panels were a hassle to remove and didn't come completely free due to the difficult electric window clips. The added wires to radio location required cutting plastic to increase space. Amp wouldn't fit in spare tire area so its under the seat. Now the good part, stereo guy maxed gain on radio to provide the amp peak power. I don't dare forget to buckle my seat belt now or I hear DING, DING, DING until I do. Sitting in turn lanes I wouldn't think to start blinker until the last possible moment or I hear CLANG, CLANG, CLANG. And I will never, never, ever leave my keys in the ignition again for the alarm is now as the church bell tolls GONG, GONG, GONG. Alas, he may have to dial down gain to get all interior sounds down to a reasonable level...unless anyone else has a fix, cause the only way I've found to drown the sound, is crank it up!...and it is sooo suhweet!!..

 

The interface used (he used one to retain the chimes, right?) has adjustments for these volume levels. No need to hurt your ears from not adjusting these pots on the interface.