This is a great topic- doesn't seem to get much airtime, even though these concerns are so central.
My Quad 57's are incredibly beamy. This is one of the prices I pay for truly wonderful sound at a fraction of the cost of comparable alternatives. I built custom stands to raise them and point them directly at the "head in a vise" sweetspot. When friends sit there, and a great recording's on the turntable they "get it" right away. It makes sense for 50% of my listening time.
Your idea of installing a high-end environmental system in addition to your sweet-spot system is excellent. I've thought of that, but I like the game of experimenting with vinatage gear too much- I'd have to choose one or the other. So I have a secondary two-channel system for ambient living/dining room social music, a 2-channel system in my studio/workshop that's got good dispersion and sounds very good with a wide range of music, even if it's not really for critical listening it's still pretty satisfying. In my one-season country house I even have a system with a pair of Bose 901's near the wall of a screen porch, which are fun with recordings with a lot of space around the instruments like dub. Talk about an ambient application- I crank these up when no one's around and have a lot of fun getting the outdoor chores done, and their great for parties as well. There's no one way to listen to great music. Having different systems configured for a variety spaces and patterns of use is, for me, the way to go. I find it interesting this approach isn't discussed more here- maybe I'm just my own kind of nut!