a wide horizontal dispersion so that someone doesn't have to sit in a precise location to hear the best sound. Budget is $1500-2,000.
ATC have wide dispersion (Dome Mid) but you will need an SCM20 or more to fill that size room....so look second hand carefully ....the only drawback is you may find you lack bass...so it would not be my first choice given your budget.
Energy also devote a lot of effort to off axis response and the top of the line Veritas (again look for second hand) can certainly fill a room of that size with plenty of bass and a very even sound field (wide sweetspot) ...probably a better option than ATC.
I suspect Duke may have a speaker that also will work perfectly for you - as he takes as much time working on and worrying about a good off axis response as other designers do about chasing flat on axis - or at least, if not his own design, I suspect Duke will have plenty of good suggestions!
Good Luck.