Sure that can be your listening room, and you are off to a great start with the Prima Luna integrated. Can you sit with your back to the adjoining room? And what about that room, is it noisy? Dead? Lively? So much depends on details one can never know without actually being there.
What we do know for sure, that room is almost square. Depending on the ceiling almost a cube. Not a problem now. Right now its not an 11x11 room its 22x20 or something like that. In terms of bass its all one room. Add in a wall though and now it really is a cube and one with the same bass modes side to side and front to back, that is to say really bad.
That said, if you do build a wall it can incorporate some really cool bass control functionality as well as a degree of sound isolation. Just go into it understanding we are not talking about your typical 2x4 sheetrock and hollow core indoor door type situation.
Do it right and you could have a thoroughly satisfying listening room. Acoustically dialed in and with enough subs it would be especially mind-blowing to close your eyes and feel you are in a huge concert hall. Which you could totally do.