Is the TV itself connected to the Bose system? IF only the Tivo box is connected, you will get no sound from the TV or anything else connected to it. Without knowing the model of TV you have, it is tricky, but if you connect everything to your tv, and send the audio to the Bose system, you should get audio from all sources. BUT if you could provide the model number of the Bose system, i can go into more detail. Also the model of the TV would be very handy!
How have you connected the Tivo to the Bose system? Optical?
K.