Chevy Tahoe Install Questions

I know this is gonna be a helluva introductory first post but I really need to get some advice hopefully from some professionals and other enthusiasts. I’m gonna try to provide all the necessary info in my initial post so bear with me if it’s long winded or if I leave anything out. To start, I’m doing a very, very modest upgrade and have no desire to shake the pavement. Those days are over for me. So, I’ll start with my vehicle particulars and then current equipment.

Vehicle:
2010 Chevy Tahoe LT
w/BOSE
w/OnStar
w/o Navigation

Current Equipment:
Pioneer AVH-P4300DVD
Rockford Fosgate Punch 500-4
Boston Acoustics S60 Components – 2 pairs
Axxess GMOS-LAN-02
Avital 5300 2-Way Security

Okay, so here we go. I’ve already removed the OEM head unit and all the Bose components except for the “sub” located underneath my center console. I have replaced all of the full range drivers with my Bostons and installed the Punch amplifier to drive them. My installer left the Bose sub fully functional at my request to determine if I would be satisfied with the sound before deciding to keep moving ahead. I guess this was silly because although I knew it was gonna sound bad, it actually sounds a lot worse than I expected. So, here are my questions/concerns:

1. My installer told me that after removing all the Bose components he had to install a small speaker behind the center console in order for me to hear my door chimes, OnStar, turn signals, etc. I thought that was the purpose of the Axxess GMOS-LAN-02. Isn’t that module supposed to allow everything to continue to be heard thru my stereo speakers or would the disconnection of the Bose amp from those speakers necessitate the installation of a new external speaker?
2. Should I be hearing a small amount of “noise” when I pause music/dvds etc. or should there be dead silence? When I say noise it’s not alternator whine or anything like that, it’s more of a very small amount of feedback I guess as a result of amplification. Just not sure if or how much of it I should be hearing.
3. When they installed the Avital 5300 they connected the tach wire from the alarm to a solenoid in the engine compartment and it TOTALLY drove my computer haywire. The car went bananas. The Stabilitrack and check engine lights went absolutely bananas. After much troubleshooting they finally determined that wire was the cause and eliminated it all together stating I didn’t need it. Can anyone advise on this? The alarm functions perfectly without the wire and the vehicle now runs as it did before.. perfect.
4. I need help choosing an inexpensive but quality pre-fab subwoofer enclosure. I’ve already decided to stay with Rockford for the sub amp. I’m leaning towards a Punch 300-1. As I said, I don’t wanna shake the pavement or draw a lot of attention to myself. I’d like to get a simple sealed enclosure with two 10’s. I found a few places online selling the discontinued JL Audio CS210-WX enclosure very cheap and I’m certain I don’t need much more than that but I am open to suggestions within my budget.

I think I covered everything. I know it’s a lot but I figured it was best to get it all out at once. Thanks in advance.