I too did this exact thing with hardware instead of doing it in Linux. I used an t.racks DSP 4x4 Mini to apply my REW-measured room correction between my sound

I too did this exact thing with hardware instead of doing it in Linux. I used an t.racks DSP 4x4 Mini to apply my REW-measured room correction between my sound card and amp, also use it to generate the split for my subwoofer.