You CAN put in any size that will physically fit. I knew someone who lived in a rented room and used Tannoy GRF speakers. They were so big he had to move one to go out his door. The real question is how you like to listen to music. If you like near-field listening large is fine. If you like a more distant perspective use smaller speakers. Of course you can sit closer to the smaller ones too. I would consider a good mini monitor and powered sub. They are less likely to overwhelm the room than a pair of large ones. I have B&W 805s and REL but there are many alternatives. They are more likely to work that a pair of large speakers but big can work. The small + sub is just easier to adjust to match the room.
how big a speaker can you put in an 11 x 11 room?
the ceiling is 8 ft but a side wall has a 6ft opening to a 25 x 15 living room. the speakers would be in the 11 x 11 room. I like the Elipsas though the bass seems as though it may be too heavy in a room this size.....same for the Revel Salon2s.....i listen to jazz vinyl through Mac electronics.....