Add remote volume control to Emotiva BasX A-100?

I am A/B-ing the Emotiva BasX A-100 and the Onkyo A-9110. One major drawback for me about the Emotiva is a lack of a remote for volume control, which I need bc I’ll be running a TV through it (not as big a deal for just music, which I can control through various apps like Tidal). I am using a Schiit Modi 3 for the DAC and KEF Q150 speakers.

I have tried to figure this out online, and the answers are murky. Is there a simple way to do it that doesn’t involve buying an expensive preamp?  I know the Emotiva TA-100 would be a good alternative, but I'm already too far down the road to go that way.

This (http://www.audiocubics.com) seems like the right idea, but is way too expensive, and would just push me to the Onkyo. I’d rather let sound quality / preference dictate my final choice.  

Any help would be much appreciated!