Adding a potentiometer

So as my idea of building custom speakers evolves…

I’ve gotten the idea of building dual Orchard Audio Starcrimson Ultras

Utilizing the separate 9V power supplies and rail capacity upgrade boards.
The idea is having one control the low end (driven by the dual 7" Epique drivers on each side) and the other the mid and treble (the AMT or planar tweeter and smaller driver on the upper portion). I would have a DAC/Pre-amp handling taking in the digital input before passing it off to a miniDSP 2x4 HD handling the initial crossover before the handoff to the monoblock amplifiers, having a custom passive crossover handle the tweeter and woofer.
The idea of adding pots to the amps is more in the idea of gain control. However, I’m not sure at which stage this should be implemented. I’d imagine I should use a dual pot potentiometer between the input and the amplifier board. Is this assumption correct? Is there anything extra I should take into account? Kinda new to DIYing this kinda stuff. Electronics, soldering and such, I’m used to. I’ve dabbled in headphone modding and making cables, but not messing with amplifiers, so I’d appreciate honest guidance.

Edit: Secondary thing that could reduce some complexity: could going for a miniDSP Flex be a better option then separate DAC/miniDSP? Didn’t know the product existed and realized it could work as a one piece solution to that stage and would allow me to go balanced.