Just got my AV and am ready to start the after-market stereo upgrads

[Dan in DE]

Just got my Chevy AV - a WBH Pewter Z71 with leather & Bose ( but not onstar ) from Shelly at Bill Heard in Nashville ... she did a great job, even though they did not make much if anything after the 3 incentives and GM Supplier discount : ).   Even though we closed on 7/31 - I just took delivery yesterday, as I am in Delaware and have been traveling.

Now - here is where I stand.  I emptied my Tundra of the after market set up it had - which consisted of:

Alpine 7894 Head Unit
Helix 400 MK II amp ( 1000 watts at 4 channels )
Two sets of Boston Rally separates
JL sub amp ( 250x1 ) - the Tundra stealthbox obviously won't work in the Tundra

I have a host of the top grade KnuKoncepts Wires & RCAs ...

So what can I do with the AV.  First the Bose is not that bad - but not great and how can I not try to use this stuff !

So - I have gone thru the archives and have read what people have done - but would like a little feedback now that they have lived with it for a while and would you do anything different.

So a couple of questions - Has anyone kept their stock HU and been happy with the results of splicing in an after market amp and new door speakers.  Were you able to keep the Bose woofer ?

Has anyone successfully put in an aftermarket HU, front and back speakers and managed to keep the Bose 'woofer'.   My thoughts no - but wanted to check.  My install guy thinks he might be able to get a JL 6 inch woofer in the same area as the bose 'woofer' - but we are not to sure what might be lurking in that area to haunt us.  This might be the ideal set up - but then I have to find a place for the two amps ( under both front seats ).  I would rather not go with a sub box in the back.

Where do you buy the harnesses to keep the door chimes etc and steering wheel controls ?

I also have a Viper Remote Start/Alarm that I would want to install - anyone have issues on this ?

Has anyone had issues with the performance of the Valentine when mounted high ( hard wired by the mirror ) - Valentine says it should work fine for rear detection - but wanted to check with how the rear window is designed  - it has the defroster.

Finally - I will be getting a Garmin 2610 GPS Nav and rather than the bean bag mount, I'd like to in hard mount.  Thinking of if I go with the single DIN Alpine Head Unit, I might be able use the second DIN ( which would be the upper one ), in making a mount the extends out from the dash so the Garmin is a little less obtrusive.  But I did notice the darn shift handle overlaps with that space.

All insights and feedback will be strongly appreciated !

TIA - Dan