Consider the Marantz SR5007 and the equivalent Denons. 2313 I suppose.
I've heard the Q300 with a few Denons and was pretty impressed.
Go for a floor stander only if the room is big. These speakers need breathing space. Both of my setups had floor standers. I have and am shifting to stand mounters.
Not having auditioned the Kefs with brands other than Denon, I can't really comment. But from whatever google gyan I have, the Marantz is a very good AVR.
The Q200 would be a good match as the center. Any make of surrounds will work.
Have you tried out other speakers?