how big a speaker can you put in an 11 x 11 room?

The biggest speaker that I would consider that could work well, if you have 2 corners available for them, are Klipschorns.

I would love to try them in my 12X12 room. Someday I may.

I have owned and auditioned both the Arro and the Ohm Micro Walsh Talls in a smallish room. Both are wonderful in their own ways, but I'm with Mapman on this one: the Ohms are ome of the great bargains of high-end audio and well worth a risk-free audition! They are also very easy to place. I found the Totems fussier.

Large speakers are designed for large rooms, and small speakers are designed for small rooms, in general. Although you can use a large speaker in a small room, often you will have an overload situation with too much bass. If you aren't that critical of a listener, as the other posters say, you can use just about any speaker. If you are interested in the highest level of sound quality, look at the Unifield Model 3, just rated by The Absolute Sound as one of the best sounding speakers at the RMAF. The UniField Model 3 is an expensive speaker designed for small rooms. Read other posts on this speaker here: http://www.audiocircle.com/circles/index.php?topic=60302.0

Sorry to go off-topic, but in light of the last post, I am compelled to comment about the Absolute Sound. Buyer beware - since resurrected a few years ago, its reviews have become overwhelmingly positive, and positive in a uniformly over-the-top way. Take any two or three consecutive issues and read the reviews - pay no attention to that man behind the curtain.

I hope you don't mind that I answer your question indirectly, but I have some advice and recommendations that I feel are beneficial for your particular situation:

Consider using the Lyngdorf RP-1 digital sound processor.
This unit uses advanced eq to correct uneven response from speakers in less-than-ideal situations. Considering the equipment you use, I guess you might be apprehensive about inserting a digital processor into the middle of your audio chain, but I'm pretty sure you'd be far happier with the RP-1 than without it.
review: http://www.dagogo.com/Lyngdorf-RP1.html

You should read Cardas Audio's article on speaker placement in square rooms: http://www.cardas.com/content.php?area=insights&content_id=33&pagestring=Room+Setup+8

Consider room treatments, especially bass traps.

As far as reference quality, top of the line, small-room-friendly speakers go, you may want to audition the following: Magico Mini II, Merlin TSM-MMe/MXe, AAD 7001i, Usher BE718, and possibly the Silverline SR17.5.

If you crave the deep, powerful bass that bookshelf speakers can't provide (even in small rooms), a pair of subwoofers would sound more balanced than only one. I read that the Axiom EP400 subwoofer (8" sealed) is more articulate than the JL Audio Fathom F113 (13" sealed), although the former doesn't go as deep or hit nearly as hard as the latter. Regardless, I suspect that the 10" JL Audio Fathom F110 is just as articulate as the Axiom EP400. For ultimate speed and accuracy (and price) the Wilson Benesch Torus is another good option, although it hardly provides half the slam of the Fathoms and it takes up more space. Of course, the Lyngdorf RP-1 would allow you to seamlessly integrate any of these subwoofers into your system.

I hope I've helped.