when an operating manual has 106 pages, it can be easier to find the connections on the rear panel than to understand how to get the CPU to let you do what you want
If there is a complete bypass of all DSP and surround processing while retaining both master volume and channel level controls when using the direct multi-channel inputs, then perhaps?
However, if you were hoping to use the internal crossover controls included in most of the latest surround receivers (even my $400 Denon has functions including Audyssey that 10yrs ago would have cost several times that for the processing /XO alone), I think you'll find they are integral to DSP/surround modes and may not work adequately for your purposes in "2 channel stereo" only.
when I managed to get my rig to work reasonably well (without rear/surrounds yet), I carefully but the manual away and try to use the cable box's remote, not
programmed for anything but volume control of the receiver most of the time - it's way too easy to accidentally push the wrong button on the Denon's control, and it can take 5 minutes to restore.
I'm sure it can do far more than I ask it to, but the learning curve ...