2 channel preamp and a/v processor setup to avoid dual volume control issues.

Unfortunately no easy way to do that , the Krell has no Unity Gain or HT bypass input.   

I would imagine the Krell's  ladder type volume control is virtually transparent,  I would just set it at a volume that is high enough to get good sound at the Mc's input on the Krell.   

I would not mess with extra cables or boxes

Use the Mc's volume for TV and movies.   Only rub is you have to make sure you lower the volume considerably on the Krell before playing other sources 

Trying to sort through the analog digital combination.  The best outcome for me would be a true analog stereo sound through my fronts (no sub) and the Roon, Chord DAC/Scaler or the turntable.  With volume through the Illusion.  Additionally, true digital surround sound through the MX 180.  Where the MX 180 is controlling signal and volume through all seven speakers including the subwoofer.  I am not sure any of these options allow for this?  Is it possible?  Thank you all for you very quick response.

JW

I believe the Illusion does have a bypass option. If I can use bypass on the Illusion how would the MX 180 digitally control the front speakers (mono blocks)?  I’m pretty lost here….

I give up.  Too much thinking after some Christmas Eve glasses of wine!