In a room with a 25 ft wall and a 12 ft ceiling, I'd say that EP600 would be good. I don't understand your second question, but making a guess, I'd point out that most people use the QS8s for surrounds with their 60s and 80s. Those of us with 50s do various things--one guy uses M3s, I use QS4s, I think someone else uses QS4s... and that's all of us!

I am the Doctor, and THIS... is my SPOON!