Depending on what you mean by large, you are wrong. Room modes are peaks (and nulls) at the resonance frequencies of the room. The smaller the room, the higher the frequency this occurs. Hence, using big speakers with a lot of low frequency output is asking for trouble.
There are five ways to deal with this:
1 use a bigger room
2 use bass traps (hard and ugly in a small room)
3 avoid low frequencies altogether, by using mini monitors (the only possiblility in really small rooms).
4 smoothen them by using multiple subwoofers
5 equalize them
In a small room the best way to proceed I think is a combination of the last three options. Multiple small subwoofers can give you enough extension for anything other than mega bang HT, and are a lot smoother than two main speakers. They can be located discreetly for best bass response and that is unlikely to be the best spot for midrange image. Avoid subs that go very deep.
Use room equalization like the Antimode 8033 to smoothen the response even further. Here, the use of multiple subs is particularly beneficial. The higher the frequency, the more localized the equalization will be. So if you start with a wider listening position by using multiple subs, you have a much better starting point for equalization. For the same reason, you do not want the main speakers to go very low.
There is one alternative to all this, and that is to use dipole speakers like the Quad electrostats (only the smaller 2815 in a room of this size). Dipole speakers excite far fewer room modes (which is why they sound so clean and neutral). However, they are pretty massive and need a bit of space behind them as well.
