short answer, about 35' and two walls.:-)
But my primary listening seat is about 12' from the speakers, which are about 10' apart, 4' from the built-ins, which total 2' from the back wall. There's another 7-10 feet behind the listening chairs. Phenomenal sound stage and bass extension (also: big speakers). When i say this i mean compared to the same speakers before i had a dedicated room, and to what i most often hear elsewhere. Yes, its very dependent on being in the center sat for a true image.
Room is slightly irregular but overall think 18' x 25', less wall depths. As i add more and more vinyl and brick-a-brack to the various cabinets the (relatively new) room is becoming deader and therefore better.
Slight toe-in, essentially each speaker aimed just outboard of the (wide) center chair's arms.
G