My room is relatively small - 13' wide by 15' deep at it's deepest. Yet I've never had much trouble getting great sound from large speakers. I suspect this is likely due to the room not being square - the symmetry broken by large bay windows - and the large room opening to the hall so bass frequencies don't load up too much.
I've had many floor standing and stand mounted speakers in my room.
Some of the "floor standing" speakers: Quad ESL 63s w Gradient subwoofers, Von Schwiekert VR4 Gen2 (full range), Waveform Mach Solo, Audio Physic Virgo, Libra and Scorpio, Meadowlark Heron-i, Shun Mook Bella Voce, Hales Transcendence 5, Thiel CS6, 2.7 and 3.7. Joseph Perspectives (for audition).
Stand mounted: Waveform Mach Solo, MBL 121, Hales Transcendence T1s, Spendor, Meadowlark, Thiel, Harbeth, and some others.
This is what happens to me every time I go with a stand mounted speaker:
"Wow, this sounds so beautiful. I LOVE it. So open, controlled, great tone...why do I need anything more than this?"
But inevitably I start to notice the deficiencies, all those times that a bigger, lower sound really makes a differences in drama, realism and immersion. And back to floor standers I go.
The thing is I've always chosen floor standing speakers that image and soundstage like champs, and I've virtually never had any problem getting to do this in my room. So it's not like I "miss" those qualities when I move from a stand mounted speaker. I pretty much get everything I heard in the stand mounted speaker, but more.
With the exception that every speaker sounds different, with it's unique tone, and I do love the sonic signature of some of the stand mounted speakers, which is why I hang on to them. I love stand mounts as a place to visit now and again, but for fuller satisfaction I need a floor standing speaker.
(Leaving aside the subject of subwoofers for now).
