If you are using the BDP-83's analog output, you are probably best served by using they analog bypass mode. As you've realized, the signal ends up going through the 950's DAC in any other mode. In those modes, the Model 950 will be applying the same bass management that it uses for any digital source. In stereo analog bypass, I don't recall what the 950 does for bass management but I think it may simply do 2.0 (no bass management at all). The 5.1 analog connection is using the Model 950's 80Hz analog bass management.

Try this: compare there stereo analog input in 7-Stereo to the coaxial or optical input in 7-Stereo. How does the bass response compare?