Amps are not IR compatible. Instead, they typically rely on a 12V trigger of some sort. Your Onkyo 805 does not offer a IR output that could trigger the 7700 (well, it has a 12V trigger, but it's for zone 2 only, which does you no good). On the other hand, it does have a switched AC outlet on the back, and you can get an AC adapter at Radio Shack that produces a DC signal high enough to trip the 7700's trigger. That way, any time the 805 is on, the amp is also on.

My wife deemed our old MX-500 remote to be the best upgrade we ever made - the M1 "turn it all on" and M2 "turn it all off" macros and the "FIXTV" button that I created for each video device (which would "fix" the TV's video input if it got messed up by accident) were instrumental in that statement. She is even more fond of the MX-700 that we're using now.