I feel you should not be contemplating on B&Ws provided you are really ready to feed them with good amplifier. Marantz oh god Bowers will never care them. Arcam 19 cannot feed the protein needed by 685S2 muscle.
Believe me I have paired 685S2 with 200 watts power amplifiers you have to hear it to believe it. In that league no speaker can come near. I don't prefer 68 series is Bowers over 600 though.
My sincere feeling / suggestion to all after having travelled this long in this hobby is Please try to buy the right speaker of your choice and try to build your set up like Amp, receiver etc., around those speakers. Cause speakers are the one which will stay with you for long.
Please don't try to pair a speaker to your Amp then your hunt will never be over.