There's a pretty good list going in another thread here in the forum, looking at the differences between the 950 and the 970. There are actually quite a few of them.

• Pro Logic IIx processing
• Dolby Headphone processing (and a headphone jack)
• a third component video input
• transcoding of s-video and composite video to the component vidoe output
• discrete speaker distance settings for all eight channels (seven full range and the sub)
• options for digital bass management, analog bass management, or pure pass-through on the 7.1 analog input
• quadruple crossover instead of triple
• RS232 port for firmware updates
• AV sync delay setting, individually adjustable for each input

That may help you make you compare the two. Also, the 990 interface does allow you to define an input as "bypass" automatically; I think the 1070 and 970 share this trait (it was a common request from 950 owners).