Need recommendations for a stereo EQ

Schiit makes inexpensive and competent 4 and 6 band equalizers. The Lokius 6 band cost about $300. It's quite transparent but I'd tuck it into a tape loop and your good to go. I do. 

Any of the Loki’s will work. The more settings you have, the easier it is to get lost 

Good luck finding a tape loop nowadaze.

Do you have a tape loop or processor loop? That’s the best way to have optional use of something, compare the changes. You need to keep the volume equal for comparison, perhaps a piece of tape with pencil marks.

Then I would start with an inexpensive multi-band eq, ascertain the changes that you prefer, that will give you info, then, move to a ’better’ unit???

I just recommended this inexpensive unit from Amazon, you can try it, learn something, keep or return it

https://www.amazon.com/Rockville-REQ42-B-Equalizer-Spectrum-Analyzer/dp/B00LZDSL7U/ref=asc_df_B00LZDSL7U/?tag=hyprod-20&linkCode=df0&hvadid=312069187648&hvpos=&hvnetw=g&hvrand=13668772867094839483&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9003512&hvtargid=pla-570384384433&th=1

BTW, years ago, I learned, it is a mistake to seek 'ruler flat' with an equalizer, just mess with it until you start learning what sounds to your liking, then work hard at refining those particular changes.