B&W 802D1 - How can I tame the brightness?

Of all the advice, getting an EQ is the worst.

Your room is a big part of the sound. Look into ways to incorporate soft items into the room. Rugs if you have hard floor coverings, etc. I’ve had luck with well placed plants like you see at audio shows.

Are you only on digital sources?  Consider adding analog.

Are you all solid state?  Consider getting a tube based preamp. 
I have friends with McIntosh gear that is warmer sounding driving 802s with diamond tweeters.  Great sound. 
 

Also note that most advice you receive here boils down to “buy what I’ve got”. Use your ears.  Investigate, try stuff. This is the fun part of the hobby. 

With all due respect to Mike, an EQ has no place in high end systems.  While trying to fix something it trashes many things. I know this sounds combative - I don’t mean it to be, but I know a ton about this subject.