Bmwmcab, my initial impression was that the OP is asking for speaker recommendation. However, after re-reading the initial post it is clear that that may not be necessarily the case. Though, I still can not tell whether the OP is just concerned about booming bass or he has already tried speakers in that room and knows for sure this is an issue. Sorry.
Regarding some of the OPs initial questions, the dimension of the room determine the modes that will be amplified or absorbed by the room. There are quite a few online room mode calculators (google "room mode calculator"). A few times I have used this one:
Room mode calculator However, one should keep in mind that the position of the speakers relative to each other and to the room walls has a bit influences on the interference pattern. The speaker ports are also very important in this regard as they are additional bass sources. There are other additional variables, e.g. material from which the walls are made, listening level, neighbor rooms, etc.. Thus, unless one measure properly the response of his/her room, nothing is written in stones. The output of all these online calculators should be considered as a starting point.
Electronic management of the bass, as first suggested by Bmwmcab, is the most effective way to go. However, if you will used speakers design to be placed near room boundaries and/or listen at low level electronic equalization may not be necessary.
