It probably depends on how hot of a room you can take before feeling uncomfortable.
I tried an XA30.5 in my 10' x 12.5' x 8' room. The room's volume is 1000 cu. ft. and the XA30.5 put out 200 watts into the room. I was sweating and irritable and returned it to Reno Hi-Fi.
Your room's volume is 2352 cu. ft. if you have an 8' ceiling. So it's almost 2.5 times the volume of mine. Each X600.5 puts out 600 watts into the room (I'm assuming that the X600 puts out the same). That's 1200 watts or six times the heat in two and a half times the space of my room.
It looks like the two 436 monoblocks put out 360 watts into the room at idle, so about 30% of the heat of the X600.
So it depends on how hot you can take it.
Can you audition them or hear them in their current setup to see what how much heat they put off?
Chuck