Upgrading from HK to BW on s60 2019

[IMAY2023]

BW are 4 ohm, so only High Performance users that need to be carefull.

Are you sure about that? 
I have full set of them from an s90 and I explicitly measured all of them.  (the yellow set) 
MIDs + Tweeters (in parallel) is about 9 ohms. 
Woofers and SUB (trunk) are 8 
Roof / pillar speakers (MID + tweeters)  is about 9 ohms. 
Center speaker (MID + tweeter) is little more than 8 ohm. 

That's why I connected 50W 4 ohm resistor in serial to my HK SUB which is 4 ohms.