Using your Onkyo and a Glo remote, would the following quoted method work out for you? It is achievable for your setup. It's a little odd, in that you press the TiVo's power button to turn on both the TV and the receiver, but press the mute button to turn off the receiver
AND the power button to turn off the TV. (One click to turn everything on; two clicks to turn everything off - but you're still using only the TiVo remote.)
What I did for a while with the Glo remote is program the power button to turn on my Onkyo receiver and the mute button to turn it off (instead of muting). That's another way to go if you want to keep the TiVo peanut and don't have a single on/off button on your Onkyo remote from which to train the Glo remote.
I don't have any recommendations for receivers, but if you decide to get a new one, just search this forum for that make and model. The Onkyos are the only ones that come to my mind that give the TiVo remote fits. It's more a problem from Onkyo's end - with separate on and standby buttons - than TiVo's.
If you could find
any remote that has a single button that turns your Onkyo receiver both on and off, you can use it to program a Glo remote. Perhaps a friend who owns an Onkyo with a single on/off button that happens to work with your receiver, or
perhaps buying and returning a Harmony 880?
Don't tell anyone in Greenpeace, but how about leaving the receiver on 24/7? $1400 pays for a lot of electricity.
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And to add to your worries -- I have to keep the Onkyo remote around to change audio sources (TiVo, DVD, etc.). My TV cycles through all of its used and unused inputs, while the Onkyo cycles through only the used inputs. I couldn't figure out a way to get TiVo's one input button to control both devices' inputs at the same time.