As a possible help to others, I just got directv service and purchased an RC66RX remote to replace the horrible RC73 that came with the system. I was able to program the remote to turn off my Yamaha RX-A840 receiver and control the audio, but was having trouble with turning on the receiver with the remote.

After a little research and trial and error, I found code 32467, which turns my receiver on and off and also controls the volume on the receiver. I don't know if this will work for other receivers, but it does for the RX-840. Hopefully this helps someone else!