in a large room with the 80's, I would consider getting an external amp for the 2600 or at least move up to the 4600 if you don't need HDMI upconversion. You would be better off with the 2600 as a pre and a rotel amp for sure. The amps on the yamaha won't compare to the Rotel.
That being said, by the sounds of it...no pun intended, you don't want to have it that loud anyways, so maybe you will get away with the 2600 on the 80's but to be honest, what you find "loud" and what I find "loud" could be entirely different. I'm in a 11x17 room, and the 4600 powering my setup has more then I'll need. But I don't exactly listen to things at 90db either.I'm more about quality then just plain loud.
I don't think the 60's would be an issue either which way. The only question is...will you wish you had gotten the 80's in the 1st place? If you can resist that temptation, get the 60's, save some money on amps and speakers.
