Digital Room Correction vs Room Treatments

That's actually not a terrible looking frequency response. I'd focus on some room treatments to try and improve bass response. I'd also (if you can) try and move the listening position to see if you can get that dip in bass to smooth out a little. If you've moved the speakers with no noticable affect, then try and move the chair.

You could also look at filling in the hole in the 40-90hz range with a subwoofer. It would be pretty easy to do and you'd hear the benefits.

Since you're mostly analog, I doubt you'd be satisfied with room correction in the long term, unless you can just add correction to the bass frequencies. You don't describe your system in detail so I don't know if that's possible or not. 
I've done a lot of experimentation over the years with room correction and I've always ended up removing it. 
Try a couple corner bass traps, add a sub, and I think you'll be 95% of the way there.

Contact Mitch Barnett or read his book on DSP (Amazon.com). I got his book and found out it was too complicated to do myself, so I paid Mitch the $750 for his remote DSP service. 

If you have DSP done by him, you should not need other physical treatment options. I had both since I had gotten GIK treatments before I contacted Mitch. I gave away my GIK treatments recently and if I ever need treatments again, I will do it digitally using Mitch's analysis.

This does not help with analog sources like my tuners but is not an issue today in my new rooms.

Digital Room Calibration Services, Convolver, Headphone Filtersets

BTW - if you are a ROON or JRiver user then Mitch's Convolution Filters are easy to use.

@rooze My room is a dedicated room for me, so there’s some flexibility in room treatments -within reason because I still don’t want it to look too wacky.  But it also doubles as an Atmos HT room and 2-ch audio room.  Because of the way my side and ceiling Atmos speakers are placed, it’s hard to move my listening position by too much without getting me out of the ideal spot for Atmos.

I’m using cheap acoustic panels in the corners (not true bass traps) and have some I can use on the side walls, but looking at REW measurements with and without, I’m not sure they’re doing much.

But I can definitely take more REW measurements with the mic in different places to see if that bass dip does smooth out.  It can either give me some incentive to try to find a way to move the LP, or resign myself to the fact that it’s not easily fixed without a sub or room correction.

I do have a SVS sub I use for the Atmos system.  With some switch boxes (I have two Schiit Sys devices), I can double up the use of that sub for both Atmos and 2-ch (I know it’s not an ideal sub for audio though).  

While I’m using all vintage equipment for my 2-ch setup, both preamps I use (Mcintosh C35 and Conrad Johnson PV5) have processor loop options for a hardware DSP solution.

One thing that would seem to work is the miniDSP Flex device which uses Dirac Live.  It’s about $750 (I guess $800-825 with tax/shipping) and I believe you can only selectively treat the frequency ranges you want.

On one hand, it’s not a cheap solution, but bass traps from places like GIK can run $400-500 each too, so I could easily spend as much or more than that on acoustic room treatments.

@yyzsantabarbara Where does Mitch's DSP insert into my system?  I'm using one of either of two preamps: a late 80's/early 90's Mcintosh C35 or an '80's Conrad Johnson PV5.

Typically, I'll have 2-3 analog inputs into the preamp (CD player, DAC, and tube phono stage into C35 or will use built in phono stage when using PV5).  Both have processor loops where something could be inserted into the signal chain to work on all inputs, but for Mitch's solution, would this have to be a computer?