Hi Didier,
I had mine in a +40m2 room and there was no problem to play loud with enoughbass.
But as always it's only your ears (and maybe yourfamily :-) ) that can decide what is enough.....
In my work-shop (2x48m2) I play a pair of JBL F12 clones on each floorwith a single 2226 under each box and that is loud beyond what is comfortablewhen the volume is turned up.
I say start with a single 1400nd on each side, you won’tbe disappointed. They are really fabulous woofers.
Kind regards
//Rob