Here are some of the most common commands:

834501C9 = Power On
834502CA = Standby On
834503CB = Tuner select
834504CC = CD select
834505CD = Aux select
834506CE = Phono select
834507CF = DVD select
834508D0 = Video 1 select

83450fD7 = Master volume up
834510D8 = Master volume down
834511D9 = Mute

- Ken