The Kansas City Actors Theatre has snagged the "Best Play" honor for two years in a row by following a simple formula. First, choose a script that's great but still fresh, something like Donald Margulies' Dinner With Friends — a show that audiences are vaguely familiar with but haven't seen again and again in every possible medium. Then cast it with Kansas City's most skilled and exacting professional actors, in this case Melinda McCrary, David Fritts, Cathy Barnett and Mark Robbins. Each is usually the best thing in a lesser show, but here they cohered into a whole fractured only in ways the script demanded. Part of the thrill was wondering which actors would be paired in upcoming scenes. Finally, appoint a director adept at movement and emphasis — with Dennis Hennessy of the New Theatre pulling the strings, these characters revealed as much about themselves walking around as they did talking. In the end, if you've accomplished all of this, the crowds will buzz with pleasure even if — as happened here — you haven't bothered much with sets and costumes. Too bad the KCAT only comes out in the summertime.