CD vs SACD in STEREO

I originally bought SACDs, a quarter century ago, for multi channel but while I still have a MC setup most of my SACD listening is 2 channel.  My Oppo 105 outputs DSD over HDMI into the HDMI input on my Bryston DAC 3.

We were cleaning rugs upstairs yesterday, and my upstairs 2 channel listening room was off limits for the day, so for the first time in a while I spent several hours in the Man Cave listening to multichannel SACDs.  I listen to classical and as an earlier poster stated the rears in a 5.1 are primarily for ambience, reflections, etc.  The pop records that I have played in 5.1 sound so much more gimmicky in their effects

I love blue meters and atmos.the new processors top of line marantz,dennon trinov,spelling, all sound great.more music is being recorded in that format. The new pink floyd is in surround format.how many times can we remarket that dark side of the moon. And you are correct sound is all around us and not just in stero this is how the ear,brain processes it. We have trained our brain for stero for decades. My surround is better than the theater so I don't get to buy 20$ popcorn anymore. Again I have several sacd players but few sacds.enjoy the dopamine in music as well, listen after  all music calms the savage beast.

@richardbrand Thank you for the good information. "Dark Side of the Moon on Pure Audio Blu-ray exploits this beautifully" was actually what got me into SACD. I know the CD and vinyl version VERY well, and make a simple setup for SACD 5.1 and bought the SACD to listen to the stereo CD and 5.1 SACD side by side. Blown away. I have not tried good SACD recordings of classical music, but plan to do so. Some SACD are disappointing (compared to the big WOW from the Dark Side). 

As mentioned several times, and as is the case for both CD and SACD as I have learned early on when using cheap store CD player to output an analog signal, and then switched to the same CD ripped to my cheap laptop, with 25 ft USB cable to (still cheap) Shiit Modi 3 DAC, the DAC is more important than I initially thought. 

How to use available DAC (in player, in receiver, separate DAC):

System 1 with Oppo 103 and Onkyo TX-RZ810 via HDMI

System 2 with Sony UPB-X700 and Denon AVR-4520CI via HDMI

Currently connected to laptop: Shiit Modi 3 DAC

on hand (not used): T763 receiver (no HDMI, only optical, coax), Musical Fidelity M1 DAC (old; USB, Optical, Coax input).

Just found that there is really no (practical, only 2 or 3 obscure ones found) 5.1 SACD external DAC. So it is either using the player built in or the receiver built in DAC. Which way to go with mine? 

System 1 with Oppo 103 and Onkyo TX-RZ810 via HDMI

System 2 with Sony UPB-X700 and Denon AVR-4520CI via HDMI