The 770 has seven channels of amplification, and I don't see any mention of back surround speakers (unless you have a quartet of ADP-470's). If you only have a 5.1 setup in the theater, you could use the other two channels of the 770 to power the outdoor speakers. If you are using all seven channels, you can pick up a two-channel amp instead.

The 950 has a second zone that you can use for the outdoor speakers. It is basically an analog pre-amp built into the 950 and as a result it doesn't have access to the digital inputs. If you were to use it, you would need to connect stereo analog cables from each source that you want to hear outside to their inputs on the 950. Then you can connect the zone 2 outputs to the amp channels driving your outdoor speakers, and control both input source and volume for the outdoor speakers separately from the indoor speakers.