I have a room with a similar size as yours and mounths ago I was in the same situation choosing between 1723 and 1723s monitors.
Both will surely do the job, 1723s monitors are not too small for the room and 1723 monitors are not oversized for the room, It depends on budget and if you think you’ll in future move to a bigger room.
Personally I went with the 1723 monitors because in future I’ll move the theatre in a larger room and they are more future proof.
I suggest you to get the 1723 monitors if budget is not a problem because you can feel the difference of having in front 8″ woofers, but 1723s will surely not disappoint you.