Listening out of the Sweet Spot - What Works?

What factors most contribute to a system's ability to portray a realistic impression of live music when listening from a separate room in the house. I've had some systems that were startlingly live sounding from another room, or even another floor. I've also have had systems that were hair-raising in the sweet spot, but once you were out of the room that same system sounded very hifi and not at all convincing. I wonder what system-specific factors determine how convincing a system is away from the sweet spot. Obviously the space, and inter-relations of spaces within a house or apartment will play some roll, but I have a hunch that the system-specific factors may play an even stronger roll. In general I've found the SS systems I've used to be more convincing from afar, where tube-based systems tend to fall off more sharply when out of the room. There have been exceptions in my experience, but in general this has held true. I am limiting my own observations to more simple acoustic music and not more complex layered music like a symphony performance or rock concert. In those cases I can't think of any systems I've owned that have convincingly created the illusion of a symphony orchestra from a room or two away. Obviously soundstage and scale is not a factor here. Anyone have any thoughts on the subject or experience to share? In turn, where is one's money best invested to create a system that convincingly realistic from other rooms in the house, or outside of the sweet spot?