Hi there.
I have the new B&W 685s2.
Before I bought these I've listened to the old 685, KEF Q300 and KEF R300. They where all standing in the same listening area at a local hifi store. They where connected to Rotel hifiset (CD-player, tuner and amp).
In my opinion the 685 are the better moniter of the 4. When I heard them, they were fresh from the box, cold on the shelve, next to the old ones. The vocals sound's on the new one beter, like the artist is standing right in front of you. The sound is quite neutral, witch my wife and I like. The KEF Q300 are, IMHO, the lesser monitor. When we where listening, is looked like the artist was 20 meters away from us, compared to the 685s2. But, like more things in life, it's kind of personal.
In the near future I want to buy a new amp. Now I'm using an old NAD 3020 which cracks a little when starting up. I want to listen to the Rotel RA 12 and the Arcam FMJ A19.
Good luck with your choice and, listen, listen listen.......
Highly recommend the Arcam A19 with 685 S2. Nicest sounding combo I've ever heard. Both the speakers and amp need a decent bit of running in to sound their best, a few hours of playing per day for about a week I found. As for the 685 S2, I did a home demo of a well broken pair of Kef LS50's but enjoyed the B&W's far more. Much better for lower volume listening too due to higher sensitivity.