my living room is almost exactly like your room. It's been really frustrating to the point I finally built a dedicated room in my basement for my primary system. I have tried many speakers in the LR though. You want something that produces deep bass and plenty of it. I also found placing them on the long wall works best for me - with the backs to the window.
I'm using vintage Infinity Monitor IIa's there now. They're set about 2' out from the window and 10' apart. The listening position is a sofa against the other wall. These speakers are flat to 22Hz, and do nicely in this configuration - though not as nicely as they do in a more optimal room. Other speakers I've tried in that room sounded like a transitor radio.
I'm using vintage Infinity Monitor IIa's there now. They're set about 2' out from the window and 10' apart. The listening position is a sofa against the other wall. These speakers are flat to 22Hz, and do nicely in this configuration - though not as nicely as they do in a more optimal room. Other speakers I've tried in that room sounded like a transitor radio.