I believe the LS50s are an upgrade over the Bowers 685.
I have owned the 685s and enjoyed them paired with the Peachtree 150. I now own the Kefs LS50s and they offer an incredibly focused
soundstage and razor sharpe imaging. However the Kefs are not everyone’s cup of tea so YMMV. Everyone says the Kefs need lot of power, this is true - you have that in the PT 300. At the current price of $999 the LS50s are now quite the bargain. I suggest you buy the Kefs online from one of the dealers that offer a 60 day return policy so they have time to break in and compare them to your 685s for a period of time to actually hear what works for you.
I have owned the 685s and enjoyed them paired with the Peachtree 150. I now own the Kefs LS50s and they offer an incredibly focused
soundstage and razor sharpe imaging. However the Kefs are not everyone’s cup of tea so YMMV. Everyone says the Kefs need lot of power, this is true - you have that in the PT 300. At the current price of $999 the LS50s are now quite the bargain. I suggest you buy the Kefs online from one of the dealers that offer a 60 day return policy so they have time to break in and compare them to your 685s for a period of time to actually hear what works for you.