So I've been looking around at the various options for digital eq with a focus on
1. usability
2. features (must be able to do M-S filtering)
3. WAF.
So far everything I have seen failed on one or more of those as they are focussed towards a fit and forget type of use, but, being sure that pro-audio has seen and fixed this problem already furtled around and finally found something that seems to tick the boxes in Calf studio https://calf-studio-gear.org/. This is a set of plugins for linux that work with JACK audio. The neat bit for me is that the 5 ,8 and 12 band parametric plugin allows each filter to set to either stereo, L, R, M or S so I have an easy way of messing around to try and find out what actually makes a positive difference for me and then decide on next steps. The bonus is that this is also midi compatible so I have a controller hooked up, so I can sit on the sofa and twiddle knobs which was the biggest usability stumbling block that I had with other options. poking a laptop whilst listening for changes is a bit fraught!
Hooked up to a focusrite Scarlett 6i6 I get SPDIF out to go into the miniDSP saving a DA/AD stage. The 6i6 may not be the greatest IO box in the world but second hand they are £100-120 so will fill the gap and work with old laptops I have lying around. In terms of a rapid prototyping capability I think it should work well, and may be good enough to be the permanent solution.
Sure those of you more studio biased will be rolling your eyes over my ignorance on this at this point
