A good room can make a bose cube sound like a line array to some people!!! (sarcasm)
Biggest mistake many make, and I have myself so I am not pointing fingers is jamming a huge floorstander in a far less than adequate sized area... Side walls are a huge issue with throwing a real soundstage, and allowing the sound to integrate at your listening position... The further away the better from my experience, or go with some decent bookshelfs and a sub.
I feel anything under about 14 feet wide is VERY limited, and normally will not allow you to use those big boys everybody wants, from Wilson to Kharma, to 7 foot tall lines.. This is because I have had rooms of 12.5 feet wide. 13 feet wide, and until having 15 plus wide never heard a room even with great room treatments anything as good as simply having the "Space"...
If your on smallish side room, or odd shape, or against all audio world grain with several obstructions and shared space type rooms not being dedicated, don't waste money on I say anything above 1500 to 2000 used, and thats even pushing it if you want your moneys worth. These are my own rules now, but believe me they apply pretty universally, however do you think a speaker company trying to make big bucks off you will really drive this home and kill a sale on thier big ticket item? They would be out of business!
Another reason so many unreasonable accusations are made of several speakers at these "Audio shows" in hotel rooms, mostly they are very limited in space, and are made to fit a king sized bed, not a speaker that belongs in an area trying to recreate a concert sized setting.