Room size for large speakers?

What would be the ideal room size for large floorstanding speakers?
I auditioned speakers that are 46" tall that sounded great in the room they were in. I got a great deal on a larger model of the same brand which is 49.5" tall so I bought them without listening. My room is about 25x15x7. It's hard to tell what a "large room" is considering that is a relative term. I'm hoping they don't overpower the room.
Depends on the speaker. Room ratios are often as important as volume. Line arrays and planers have less ceiling interaction than dynamic speakers--so this can affect what ceiling height might be appropriate. Construction techniques can also affect overall acosutical volume--for example a stiff wall will make the room acoustically hold energy and thus reduce it's effective volume, where as a flimsy wall will leak energy. How the room is engineered also has a huge effect.

I realize I haven't really answered your question--but that's because there isn't one ideal room size. I'm glad you asked the question though because we get this question regularly--or similar types of very open ended questions like "what's the best room dimensions?" without any other qualifiers. Again--those types of things are dependent on many additional variables.
I have a 23x23x9 sized family/audio/theater room with a pair of Verity Audio Parisifal Ovations. They KICK BUTT! They have no problem filling the room full of energy filled music.

My experience is that there is a dranatic improvement between "bedroom" sized rooms (12 by 14 feet) and rooms in the 20 foot range. After about 30 foot size you still get improvement but diminishing returns. Much greater than 50 feet becomes a problem becuase of large delayed reverb IMHO.

Of course as Rives correctly implies... a good treated small room may sound better than a bad untreated mid sized room...
IMO many are way to quick to advise on small speakers, they can be and are great but nothing compares to a large speakers scale. I am in a 14X24 dedicated room and run near 6ft tall speakers with 3 10' Woofers, ribbon mids and tweets. I am only saying if you want a large floorstander you should ofcourse audition one in your room and not dismiss a particular speaker based on matter what size speaker audition is always a must.
In a thread I had initiated back in June '06, I had posed a similar question. One informed individual advised that in THX terms, a large room would be anything over 4500 ft3 in size and any room under 3500 ft3 would be considered small. So I guess medium is in between these two. But this remains subjective and open for discussion. Opinions can vary of course.