I have pretty much the same setup, 55" w/ 9'-6" to my eyeballs.I have a 55" LED 1080p TV and sit about 10' from it and find myself moving closer for things like gaming. I sit about 5' from it when I am playing first person shooters.
THX calls for 100" TV's for our distance. Per my experience with my cousin's 120" projector screen at 10'-12', I concur.
(My TV is the biggest I could fit on the wall. It only has a 10" buffer on each side - to an interior corner on one side and an opening on the other. I also accounted for a slightly wider TV bench below it to serve as a physical barrier to keep little kids from touching it - it is only 6" proud of the TV on the sides but is maybe 18" deep. -What I'm saying is my TV is too small and I want to put in a home theater room in the basement.)