Bower and Wilkins Retrofit -Volvo XC90 2025

[IMAY2023]

When does series 2 start?

I think it started from 2023+. 

  Th HK has no tweeters in the rear door.Is there a chance wiring is there but unplugged?  If not there ,is it possible to install new wiring and does anyone know the amp output for those tweeters?

This is strange. It should have the tweeters maybe not the MIDs.  Wiring depends on the production sometimes they are pre-wired and sometimes they are not.  
Removing the door panel is very easy. Check the existing wiring How many channels are coming in.  If there is only one, you can connect all (Woofers, MID and Tweeter) in parallel via balancer just make sure not drop the total impedance below 4ohms.  If you have two channels coming in, you can connect tweeter and MID in parallel. 

If HK is 4 ohm,I can also go the aftermarket route and install new speakers from Hertz/Focal/Audison.

 You can always go after market.  Some folks here done that.  

On the HK, for front doors. Each speaker has its own output 

May not be true for HK.  MID + Tweeter might be in parallel. You can check and verify with multimeter.   

What about center speaker.  Can it be wired to the HK amp? 

You already have a center speaker output coming to the dash from the HK amp. You can simply replace the HK grill with the B&W grill and buy GEN1 (yellow) B&W center.  You can find used ones on ebay. Even from Aliexpress.