So I am swaping out everything from front to back. I do not know much about our HHRs yet and I can't seem to find what I'm looking for in the search bar.
How many amps does my car have? If it's one, is it a 5-channel? Or does the headunit power the doors/tweeters and a 1-channel amp power the subwoofer?

 

The sub does have it's own amp.

 

How are the door speakers and tweeters powered, external amp or by the headunit?

 

Actually the amp mounted to the sub box is 5channel and powers the doors and sub.

 

Great thanks. That was exactly what I needed to know.

Where are you splicing into the factory harness for the door speakers?
I'm thinking I'm just going to hook the door speakers to the headunit and run the 8inch sub off a small mono-amp like the Alpine MRP-M500 or something similar.

 

Ok so I went to talk with the installers at Best Buy. From what I got from them is the LAN-04 will integrate my new Alpine to my factory amp. Will I lose sound quality that my Alpine would be putting out? Can I still use the equalizer on the new headunit to its full ability?
Or am I better off bypassing the factory amp all together?

 

Are you talking alpine amp or head unit?
I thought you were swapping everything out. If so, the factory amp really isnt worth keeping, its only about 25w per speaker.

 

From the info you told me about the factory amp, I am going to bypass it all together and just use the Alpine headunit to power my door speakers.

I am assuming bypassing the factory amp is easy? any input would be great.

I already have the GMOS-LAN-04. It is ment to integrate the factory amp. Can I still use this harness if I plan on bypassing the factory amp?