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

I fought a brightness battle with my B&W 801 Matrix speakers. I then fought a similar battle with my Wilson Sasha 2s. I now love my Rockports. Save yourself the battles. Sell them and find a sound you love.

+1 find a sound that you love.  A speaker that will draw you into the music, a joyful place like no other.  Move on, this one ain't it.  

You haven't mentioned any room treatments. For sure I would treat the first and secondary reflection points.  I've used GIK art panels and further added Owens-Corning insulation to this with excellent results.  My hearing is sensitive to high frequencies anyhow and this made a big difference for me.  This will improve the sonics in just about any room and no matter if you change speakers, it will improve your sound.  Also agree with the others regarding toeing the speakers straight out and not in.  

You might look at using Marantz gear with the B&W. Marantz lean toward the warm side and can help tame those speakers 

Op Audioquest waters interconnect are on the thin side, try Columbia Audioquest or maybe Cardas. Cerious graphene cables might work.you can audition them too.