B&W DM603 + DM602.5 + LCR600 vs KEF Q5 + Q3 + Q9c

I'd take the B&W over KEF. I've A/B'd Monitor Audio side by side with B&W and the older silver 8's had better quality of bass. Faster, well defined, more musical. Maybe B&W better for home theater? I don't know.
B&W with Nautilus tweeter tube was much less boxy sounding than Monitor Audio.

I auditioned the B&W series that you are interested and at first I thought they were very nice until I auditioned a pair of Monitor Audio Silver 8 along with the Silver LCR center. IMO they destroy the B&W DM603 + DM602.5 series speakers. For home theater the Silver 8s are incredible! For music I am very satisfied, very tight and fast bass and unlike some response the speakers are not bright given you pair them with some good cables. I am running a pair of Wax bi-wire from Zu Cable. If you want to spend a little more go for the MA Gold Ref 60s. All I can say is they are absolutely incredible. As for KEF I have never auditioned any of their speakers.