1. As psyprof1 pointed out, any of the input buttons will turn the 990 on. It's done to provide discrete on and off codes - hugely handy in creating macros on univeral remotes. For example, my MX-700 has a macro on the "POWER ON" button that turns on the TV, then turns on the cable box, then with one signal turns the 990 and and sets it to the cable input, then sends a signal to the TV to make sure it's on the correct input (a discrete code for the TV that sets it to component 2).

2. Many people who are used to a 5.1 setup get confused about side and rear surrounds. If you only have a 5.1 setup, your surrounds may be mounted more to the rear than to the side (although THX and Dolby still recommend the speakers be located on the side walls). That does not mean you will use the rear surround outputs. If you have a 5.1 setup, you will want to connect the surrounds to the side surround outputs.

3. That one I'm not so sure of. There are some other threads floating around, and I've heard about folks using a search command with a DirecTV box to find the right code.

Glad to hear that the 990's working out for you! It's been a piece of equipment that I've enjoyed for over a year now and that is clear enough to use that (with the help of my MX-700) my wife has no trouble using the system on her own.