Indeed. I'm looking forward to hearing separates over my old avr.
I would just go with a Marantz, Denon, or Yamaha flag ship or near flag ship AVR without the amp. Then if you find that lacking, add a 2 or 3 channel. Your room is not that big, so very likely an AVR will do just fine, the saved money can then be spent on things that count much more. Their isn't much point in matching the LS50 with big amps and KEF recommends 25 to 100W. Anything like a Denon X4000, AVR-4520, Marantz SR-7008, or Yamaha RX-A2030 should be all you need for them to sound great.
If you must go separate, then my vote is also for the Marantz, I am very happy with mine, they are quiet, run reasonably cool, dynamic and reliable so far.