Room Acoustics and Speaker interaction.

No_regrets, why would you want to put speakers in her room? Would you like if she was putting things she likes (e.g. shoes) in your dedicated room? :)

IMO, both Luvs2listen and Bob_reynolds have given very good advices. For speakers, I would recommend Dynaudio sealed monitors e.g. Audience 42 sat or Contour S R, complemented with a sealed subwoofer.

Also, whether or not you will excite any room modes, it depends on how loud you are listening. For soft listening sessions you may not excite any room modes, so your square room may not be a problem after all.

It's your room not the speakers

The OP did not talk about any problems, only asked opinions about speakers that might work fine in his small room. While I agree that electronic correction/equalization can do wonders, it is naive to think that you can put your speakers anywhere in the room and then get away with this by running the room correction set up procedure. Electronic equalization should be used as little as possible, i.e. you put the speakers and sub in the best place possible and then run room correction set up procedure.

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.

No-regrets, if the wife is ok with he Tannoys then I would try them again only this time stuck something into their ports, e.g. some foam or sponge, rolled socks will also do.

Keep in mind that the density of the thing you put into the ports will significantly affect the bass output of the speaker, i.e. the denser the material the less bass output the speaker will produce.

It just didn't sound right. It lost its naturalness, it's intimacy, and to my ears, I didn't like it.

I know what you mean No_regrets. You should try to use something softer, also do not stuff the speaker ports. The speakers need to "breathe" a little beat.

Of course, I am not trying to stop you to buy new speakers. That is always fun!