...plus an external amp, usually. BUT, you can get one that drives 9 channels, and processes 11 (the Denon X3600 is the cheapest I know of) , so that, in the future, it can be added. Have the room prepped for 7.x.4, if you want, then you have the option.
You can do a pretty good setup there. I'll contribute more, but I won't have enough time until later. Maybe someone else will chime in before then.
A couple basic thoughts. in a 5.x.x system, the surrounds go on the sides, not the back. Common misconception. in a 7.x.x then you add a pair...