I always set my volume on the pre/pro to -5 and set the SPL meter to 70dB and try to center the needle on the zero mark of the meter. I feel this way allows me to dial things in a little better as the marks on the SPL meter are larger and more precise in this range. When the volume is adjusted to 0dB you still end up with 75db using this method as well. The marks just get harder to read towards the sides of the meter where the +/- 5dB readings are.

I always had a hard time getting the bass dialed in with the 990 for both 2-channel listening and movies at the same time. I could get one, but the other sounded too bassy or too lean. The stereo offset helped, but the issue was never fully tamed for me until the implementation of the SMS-1.