I've got some comments in my 990 review that might help a bit.

The two units behave differently as far as selecting the multichannel analog input. The 950 has a "6CH" button that switches to the multichannel analog input, and the next time you select a new input it switches away from the 6CH input - you don't have to manually switch it off. The 990 treats the 7.1 input as a separate, individual audio input, which also means you don't have to switch it off to go to a different source - just select that source and you're there.