Topic: Controlling HDSPe AES level

I have an HDSPe AES that I'd like to use for my main out. It's attached to an ADI-8 DS, giving me 8 analogue outs.
I'd like to control the volume of these analogue outs. Now of course TotalMix FX can do this, with fader groups.
But I'd like a hardware control, not use the mouse. What are my options?
My guesses:
- MIDI: the AES has a MIDI port, but there's no basic one-knob MIDI controller that I can find. I don't want a whole surface just to control output level.
- OSC: I know nothing about this - it seems to just be for mobiles and tablets though?
- Eucon: May not work, and even then, there's no single-knob controller out there either.
- Keyboard? Is it possible to hack keyboard shortcuts somehow so they work even when TotalMix FX is not maximised?
- Windows volume control: Is it possible to link this to TotalMix FX?
- Other software, eg Girder, Autohotkey or similar. I have no idea if TotalMix has a way of being accessed by these.
- RME's remote controls. I understand these can only work with the USB series - correct?

Many thanks,

K