I'm trying to achieve the best sound from stereo sources via the Oppo into my 950. I want to use the 950 in 7 Channel Stereo mode and feed the Oppo stereo analog outputs to the 950 CD analog inputs. (I also read the Oppo stereo DAC are a little better then multi-channel DAC.)

I achieve the audio but the 950 CD input bass response is vastly inferior to the signal from the Oppo 5.1 analog outputs feed to the 950 5.1 analog inputs. The 5.1 connection is a much deeper, richer sound (the sub is much more active) while the high end is roughly equal. The Oppo setup has all speakers set to "large" so no bass mgmt should be occurring there. I thought the same basic bass management would be applied to both the 950 analog CD input & the 5.1 analog inputs (with bass mgmt "ON"). I know the CD input is converted to digital in the 950 for processing but should it pull down the bass response? Am I missing something else that occurs in these configurations?

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?

I want to do pretty much the same, but my question is if one is using multi-channel outs(SACD, DVD-A, BluRay, DVD) AND stereo outs (for the superior stereo DACS) does the OPPO know to sent CD data through the proper outs? Is just switching at the processor the answer? I don't find any setup with the OPPO regarding this.

All of the BDP-83's outputs are active at all times, unless prevented by the source (which is basically a single scenario: SACD's can't be output via optical or coaxial due to copy protection restrictions). The stereo output always provides a stereo signal, including downmixing immediately before the stereo DAC if the source is multichannel.