I am indecisive about choice due to room size

Square rooms should be avoided. You will have a hard time overcoming the limitations and acoustic issues of a square room by upgrading any of your components. If the spare room is your only option, I would seek help fro GIK before doing anything.

J.Chip

Two questions:
1) Have you specifically identified what you think is inadequate about your existing speakers?
2) As others have noted, a 12X12 room is problematic from due to standing wave issues at specific frequencies. Do you have any acoustic room treatment installed? If not, you might consider that first.

"Sit 2’ from your speakers and listen to them. The difference between that and your chair is room acoustics."

The difference is the speaker’s off-axis response plus the room’s acoustics. 

Duke

It is always interesting when someone says they love their speakers and want to upgrade..please don't tell me you are looking for more bass. Everyone is looking for more bass. I would guess you are looking for a rich textured mid-range with good front to back layering and you would like the speakers to disappear so you are left with just the music. 

The Charney Audio Maestro would be a perfect fit for your room. Charney designed the Maestro specifically for smaller rooms. I happened to be at Charney yesterday we listened to the Maestro with Lii Fast8 drivers ($2800.00) in his 14x19x9 room. Although the room is too large the Maestro put on a great performance. Very open soundstage, pinpoint imaging, with adequate clean bass. The Maestro maintains all the goodness of the upper tier Charney offerings just designed for a smaller room friendly platform.

The Lii Fast8 is a new driver for Charney and the site hasn’t been updated yet.

http://charneyaudio.com/the-maestro.html