@soix
A little follow up. I upgraded the original RCA 12SN7s with some NOS JAN Sylvania VT-231/6SN7s from the great folks at LTA. They're sounding better every day.
After getting a remote, I went directly from MZ2 to A23+. To have enough play on the LTA volume control, I had to use the volume pots on the amp. So I essentially swapped the volume control on Kara for another. After a couple of weeks, I've switched back to running the MZ2 through the Kara with better results. I think the RL volume on the Kara is cleaner than the volume pots on the A23.
So the amp runs with no attenuation, the Kara provides resistor based attenuation, and the MZ2 volume control is just right. I can always run the Kara wide open and only have the MZ2 volume control in the chain but I think the gain structure is better with some attenuation. I can also put the Valhalla 2, or a vintage pre without remote, into another input for another flavor. And I have the SS functionality on the Kara for non critical listening. I like it.