In my opinion, you're just used to the way your B&W's sounded to you, for 15 years of use. You're ears and brain may adjust over some time to accept the new speakers.
I've tested identical speakers, one set new out of the boxes and the other with 2+ years of use on them and found no difference in sound signature.
Overall, if you're not happy with the sound of the new speakers, you may never be. At least you're in a good position with them so you wouldn't take a beating if you were to re-home them.
Maybe a newer set of B&W's would benefit you. (??)
I've tested identical speakers, one set new out of the boxes and the other with 2+ years of use on them and found no difference in sound signature.
Overall, if you're not happy with the sound of the new speakers, you may never be. At least you're in a good position with them so you wouldn't take a beating if you were to re-home them.
Maybe a newer set of B&W's would benefit you. (??)