The Luxman integrated has a preamp input which I feed from the front channel precuts on my surround sound receiver.  When I switch from the preamp in the Luxman to the external preamp

Input, the Super Nines are my front speakers in the 7.2 surround sound.. Some amps have Home Theatre By-Pass which accomplishes the same thing. When I’m listening to music, the SS receiver is off and the preamp in the Luxman is back in charge. I’ve used the preamp inputs to connect a tube preamp - which I liked a lot , but I’m kind of constrained by my limited shelving. I’m thinking of changing the cabinet where the turntable is - to Hi-Fi shelving, to give me more flexibility for adding and changing.  My current set up is such that hooking up cables is a real pain. 

I was raised on Linn equipment in the 80's. so you'll have to excuse me - but I wonder about the effect the speakers not being used (from the home theater set up - center, surrounds, etc.) has on the sound of your system when you are only playing the stereo. Back in the day, it was deemed important to remove all unused speakers from the listening room lest they vibrate in sympathy and negatively affect the sound. The recommendation was if they must be there, that the unused speakers be shorted out with a wire. So, I wonder about that.

And I wonder about the rest of your room, and whether there are enough absorbent surfaces to keep the sound from feeling shouty or a little aggressive. It may be fine - your images show only a small part of your room. Again, you have great equipment. You'll dial it in over time if you haven't already...

David