Room size definition

I would like to better 'describe' (or specify) my living room when people I ask for input want to know about my 'room size'.

My living room is 25 x 15, very open on one side (25). 2 stories high (19'). 

Speaker placement is 2 ft in front of short wall (which has 2 open squares 4x5 (open to breakfeast/kitchen area on eye height), one in corner, one in 'open corner'. Listening about 15' from speakers.

18" Dayton sub in sealed encloserdriven by Elemental Design LT1300 amp (Built for eD by Keiga and based upon an ICEPower module developed by Bang & Olufsen)  is providig low bass (sufficient for my taste/need). 

I currently run the smallish front tower speakers in 'small' setting' (I found it improved the sound vs 'full range', even when I had true full range tower speakers).

I am now considering smaller 2 way speakers, like LS50. 

Concern: can a LS50 (with sub) or similar speaker with small drivers 'fill' the room (i.e. provide SPL in realistic levels)? Alternatively, I consider a (used) B&W Nautilus 804.