Yeah I found your issue, its the plaster walls, even though your walls and ceiling has great sound proofing, your not getting an open sound stage or reverberation because of those plaster walls. So it depends on how open the room is, your dampening the sound stage dramatically. I would add a couple multifusers to your sound stage. It provides multi-reflection on both vertical and horizontal planes in sound critical spaces. It performs on mid and high frequencies, brightening and clarifying sound. Thats what I would start out with. Happy Listening! Ralph