There was a chart I came across once that someone had posted and it appeared to come from the Klipsch web-site. It measured speaker efficiency versus sound pressure level versus amp power required. It was pretty interesting since they way I read it, I needed 64 watts for a 90dB speaker to hit 108dB at 1meter, or 256 watts for the same to hit 114dB at 1meter. Since I have a mix of 8 ohm speakers that run from 88-91dB, I found this chart close to what I was thinking, finding an amp that would give me 200 clean current watts. That would put me not high on the dB peak scale, but more like accurate and a good full range response to all my speakers at easy listening levels. With the 770, this is what I am getting.

For your reference, the same chart lists a 102dB efficiency speaker as needing 8 watts to reach 114dB at 1 meter. You might be better off running these klispchs off just the 1050 or something like that. I have seen other posts on the internet about people using 30watts to power the woofers and then only needed 3-5 watts to power the mids and highs in these klipschs.

As to your other question, you will not hurt the amp or speakers if you matt a 200watt channel with these highly efficient speakers. As long as you don't clip the outputs, you are safe.