Can I ask if there is a specific reason for looking at the 686s? If I were in your boat looking to replace a pair of missions (which funnily enough I am - see my other post re speaker problems to look out for) then I would probably consider the MA BR2s as well...
As to whether it will be worth booking a demo, watch this space. I've got mine booked for tomorrow afternoon and will report back!
1st off, BR2. Nice upper mid and treble, but the boxy boom in the upper bass was too much for me. Not much more (if any) detail than my missions. This lead to
2) B&W 686. Didn't rate 'em I'm afraid, unless at far higher volumes than I like, when they sounded ok. But having a 6yr old daughter in the bedroom above the lounge precluded them. Still don't think they were a major improvement on the missions though
3) KEF iQ3SE. Cleaner bass than the BR2, but "cuppy" sound to the vocals.
4) Was going to go for the BR5s, but for decided to audition a pair of RS1s, as they were on offer ex-dem at £279. Now we were talking... much better separation of instruments and much better clarity. I still felt they were a little lacking in bottom end though.
So, I hear you asking...conclusions and what (if anything) did I buy?
Well, conclusions is that the current crop of £2-300 speakers will not worry a decent set of missions.
...but a set of Oak RS6s ex dem (1 week old) at £449 were far too good to pass up ))
Time to change my signature at the bottom methinks... naah, sod it, I'm off to listen to some records!!!