Just hooked up my new Schiit Lokius. Very happy. My room is a little bright and needs just a gentle high end roll off, plus I use the 20 Hz band as the bass blocker to my main speakers ( bookshelves) to clean up when I really crank on them.
I run an Antimode Cinema in line with my sub for a little DSP where it can help without hurting. Quite happy with it. ( includes a mic and does automatic setup) . Knocks down a couple peaks which is about all we can hope for.
To just try things cheap, the JDS Subjective is similar to built in tone controls, 3 band, Mid-grade op amps. $99 Don't laugh at it because it is not a boutique mega-buck in a billet case with dealer markups and big audio show budgets. It is what should be built into any pre or integrated amp but the subjective reviewers with nothing else to do convinced the "esoteric" market they are evil so they went away along with balance and loudness, rumble filters and other actual useful features. Bitch, bitch bitch.
Lokius is a big step up. It uses tanks, not op-amps. Without going DSP, there are not many other options that can even get close to good mid-fi, let alone what your AR/VT stuff provides. They do have a trial-return period so very low risk.
All these have bypass switches so they don't need a tape loop like in the old days. Just put it between the pre and amp.