Which speakers, if any, combine the strengths of Harbeth and ProAc ?

What are the strengths of each brand that you are looking for?

I've owned 3 Proac models and subsequently 3 Harbeth models over a period of about 30yrs.
I've owned ATC for the last couple of years.
While they have all been fine speakers, I've found ATC to offer superior timing, dynamics and broadband neutrality built around engaging and realistic mids.  
For me ATC are the more flexible, in the sense of sounding confident and convincing with any type or genre of music - classical/jazz/rock/electronic etc - which suits my eclectic music tastes.

Rockport and Verity Audio come to mind.

Verity and Reynaud

+1 for Vandersteen. I owned Harbeth speakers for years, various versions of the SHL5 and the model 40. I also had Proac Response 3's. For me the Vandersteen's do everything the Harbeth's and Proacs do well and build upon those strengths. My advice too you would be to go listen to any of the speakers recommended in this thread. Your opinion is the only one that counts. Good Luck!