From what I've heard from others, the 970 and 1070 seem to have made some good improvements over the 950 on signal acquisition time. I don't know if it is as fast as the 990, but it doesn't appear to have been an issue for 1070 or 970 owners.

The 970 handles channel trim the same as the 990 and the 950 - it's still a global setting. The 970 does offer the same two-channel sub offset that the 990 has (allowing you to dial down the sub up to 8dB when playing in a stereo mode).