What makes a speaker too big for a given room?

Money.

What Stanwall said. If you cant get far enough away, then you might hear each driver seperately instead of as one wavefront. Some time aligned speakers are designed with a certain listening distance in mind. Also, bass notes have a long wavelength, some exceeding 20 feet, so a 25hz note might not even create a single wavelength before it bounces off the rear wall and back on to itself.

Small rooms are better suited to stand mount monitors. I use a NHT Classic 3 in a 11 x 11 room with good success.

It's obvious you guys have never been to Japan !!!! Tiny rooms and humongous speakers are seen more often than not. Like the poster above said, worlds largest headphones !!!!

Some explanations never make se.se to me, here is my question. If I have a monitor speaker with a added sub I get 20hz full range bass, now I can also get a 5ft tall full range floor model that in itself goes to 20hz. Now if my room is considered small people will say go with my first option and may say NEVER consider option 2. But 20hz is 20hz right? So why is one idea too big and other isnt??

I have a question similar to the one posed by Chadnliz. What is the difference in performance between a full range floorstanding speaker and a monitor speaker from the same model line that has the same tweeters and mid range drivers, used with a seperate sub? Is one setup one 'better' than the other. Pros and cons?