You mentioned twice there isn't any side wall on the right side since it's an opening to the hallway, and on the other hand you stated the the right speaker is 1.5' from the side wall. So, which is true? If there is no side wall on the right, the width of your room isn't exactly 12' and that may allow consideration for bigger speakers.
At any rate, I generally agree that monitors on stands coupled with a subwoofer is a better option in smaller rooms to avoid overloading of the room that may cause boom. Small bookshelves often sound better in small rooms with pin-point imaging but a subwoofer(or a pair) is necessary to complete the package. Your friend's recommendation on the Proac Response D Two is a good one. I am not sure what is it that you dislike about your current Linn Katan but the Proacs are really good speakers. I just acquired a 2nd pair of Proac Tablette 50 Signatures and found them to be very musical and engaging. A subwoofer is a must for these speakers even in small rooms. I have them in a dedicated room with diffusors on front wall and absorption panels on side walls and these small little speakers sound quite amazing. Good luck.
At any rate, I generally agree that monitors on stands coupled with a subwoofer is a better option in smaller rooms to avoid overloading of the room that may cause boom. Small bookshelves often sound better in small rooms with pin-point imaging but a subwoofer(or a pair) is necessary to complete the package. Your friend's recommendation on the Proac Response D Two is a good one. I am not sure what is it that you dislike about your current Linn Katan but the Proacs are really good speakers. I just acquired a 2nd pair of Proac Tablette 50 Signatures and found them to be very musical and engaging. A subwoofer is a must for these speakers even in small rooms. I have them in a dedicated room with diffusors on front wall and absorption panels on side walls and these small little speakers sound quite amazing. Good luck.