@prof agreed that big speakers can work in smaller rooms - there may be limitations to their ultimate performance but even then they can sound better than smaller speakers. The issue as you point out is that you can't really say for sure until you put those speakers in that room. To the extent that a set of speakers has the ability to tweak output (whether through jumpers, resistors, etc.) that certainly minimizes the risk of not having a speaker work well in a room that is smaller than typical for that speaker.
