Adding DSP to existing system (all balanced but a sub)

I think Roon is the obvious place in your setup to add in digital room correction. Roon Muse allows you to add either PEQ or Convolution filters.

If you have an iPhone or iPad, the cheapest, dip your toe in the water, first option, is to buy the HouseCurve app. You can just use the built in mic in the iPhone/iPad and create some PEQ filters to try in Roon.

The second option might be buying a UMIK-1 USB mic and using the fantastic donation-ware software, REW (Room EQ Wizard) to create either PEQ or Impulse Response filters. The Impulse Response filters run in the Convolution filter that you can add in via Roon MUSE. There is a bit of a leaning curve to using REW effectively, though.

A third option, that I’d recommend, if you have the wherewithal, is to buy the UMIK-1 and then purchase Focus Fidelity. It will do a far better, easier job than trying to learn the intricacies of REW.

I own Focus Fidelity and know a fair bit about REW but Focus Fidelity does a better job in my system with far less stress.

Good luck with it. It is worth the effort.

Kind regards,
Peter

PS No affiliation with any of the above.