There are some single driver systems that are reasonably compact that have the dynamics, life and texture of horn systems, but few have the reasonable tonal balance and relavitely mild horn colorations of the AGs. Good horn systems, like Edgarhorns, also are reasonbly free of coloration, but they are also pretty bulky. Still, you should look into Edgar Titans.
Classic Audio Reproductions makes some original speakers and reproductions of classic speakers, like the JBL Hartsfield, that sound pretty good. I heard one of their original models (D-1, D-3? I can't recall the specifics) that sounded pretty good and were not that unwieldy or strange looking.
I quite liked DeVore's Super Eight speaker that I heard at The High End Show in Vegas. This is a compact floorstanding multi-way speaker that, while not having quite the incredible presence and life of horn systems, was not the constipated, lifeless lumps of BLAH, that so many current speakers have become.
The French company Triangle makes a whole range of reasonably lively sounding speakers, but they can be bright and thin to some tastes. Still, they warrant an audition.
Another reasonably nice speaker that is quite compact, nice to look at and very versatile when it comes to placement is the Gradient Evolution.
I also like Gershman's GAP 828 speaker, but, it is a bit big and somewhat weird looking (essentially an obelisk with the top half bent forward).