I am the OP but I threw out my throw-away account. I don't use consumer AVRs; I use pro-audio equipment for producing the content consumed on consumer AVR equipment. I tried some of these fancy boxes that you upload EQ curves to for room correction (such as different MiniDSP-branded correction boxes which are very popular) but I've gotten measurably best results (with my measurement mic) using old-school 31-band graphic equalizers that have the 31 physical fader sliders you move up and down. These old-school analog devices have lower latency in milliseconds than the hi-tech DSP stuff which needs extra time to buffer and process the signal in ram. The fanciest digital correction available in those AVR type devices (such as Dirac brand correction) delays the entire signal by as much as 100+ milliseconds (making gaming and live instruments impossible because the audio lags so far behind the event that produced the audio, like how thunder lags behind a lightning flash). The theory is that because a 20Hz frequency has a 50ms cycle-time, you need to delay the audio signal at least 50ms across the entire 16Hz-20KHz spectrum to "see" what you are correcting down near 20Hz. However, multiple blind listening studies have shown that the human ear is not time-latency sensitive to the lowest base frequencies. These frequencies are "felt" more than heard and the brain lags with letting you "feel" the deep rumble. Old-school analog equalizers only delay the actual low-frequencies that correction is applied to (the frequencies you actually slide up or down on the physical slider/fader controls). So if you slide the 50Hz fader then only that frequency has its timing altered, and the brain can definitely hear the loudness correction at 50Hz when Godzilla roars or the earthquake in your movie happens but it can't hear the timing difference if you delay the 50Hz wave slightly in order to correct its loudness. So you gain loudness accuracy (which you can easily hear) at the expense of timing accuracy (which at low frequencies you can't hear). Also, I'm really picky about speaker hiss and a good 31-band analog EQ introduces less noise/hiss than more expensive digital EQ boxes I've tested. I put my measurement mic right up to the tweater and recorded the hiss that the digital box made and took a screenshot of the spectrogram, then compared with my analog EQs and my analog EQs were better, noticeably enough that I didn't even need the mic in order to hear the hiss difference.

So my advice is to get a UMIK-1 measurement mic and a 31-band graphic EQ, then download roomeqwizard.com software and learn to use it. It involves walking around your room with the mic while playing constant test tones and watching a sound spectrogram graph on your computer screen. Even though the test tone is constant, when you walk around your room with the mic you can see and hear how the tone changes due to the standing wave phenomenon. It will open your eyes (and ears) to how the room you are in affects the sound coming out of speakers. And rather than reading articles on the web you can actually experience for yourself the scientific reality of how it works, just like in high school chemistry class you see what happens with your own eyes when you mix vinegar with baking soda, rather than just reading theory in a book. The actual physical experimental confirmation is crucial.

Adjusting anything over 250-500Hz is a waste of time because if you shift your head (or measurement mic) just a foot or two you get a completely different frequency response. When you test this yourself you won't need to take my word for it or read web articles shilling snake oil audio products. Your eyes and ears and calibrated measurement mic will confirm the scientific reality for you.

As to other equipment... at the affordable lower end you want a USB or Thunderbolt interface with balanced XLR connectors connected either directly to studio monitors or to an equipment rack with the amps, crossovers, equalizers, etc needed to power big passive subwoofers. The Focusrite Scarlett 2i2 (~$160 on Amazon) is a best seller USB audio interface and crystal clear. I'm listening through one right now and I love it. Be aware that if using a Mac with a T2 security chip (2016 and newer Macs) you need to use an external thunderbolt USB hub because T2 occasionally cuts out the internal USB; scroll down this article if curious:

https://tidbits.com/2019/04/05/what-does-the-t2-chip-mean-fo...

Here is a screenshot from the article of the T2 hiccup actually being recorded: you can see the audio waveform briefly cut out:

https://tidbits.com/uploads/2019/04/T2-hiccup.jpg

None of Apple's "fixes" fixed the problem. This was the last straw for me and many other audio guys so now we use both Ubuntu and Windows 10 with WSL instead of the Mac. Most photos of $1M+ recording studios I see nowaways have Windows 10 desktops. If you don't want Win10 telemetry spying on you you need to set up a pi-hole or external firewall box, but M1 Macs and all iOS devices report your location and other telemetry to Apple now so you also need an external firewall for Apple now too, but I'm digressing from audio....

Back to audio, the UMIK-1 USB measurement mic is usually ~$99 new on Amazon/eBay/wherever. The roomeqwizard.com is free (as in gratis, not open source) Java software that can use the mic. For studio monitors, Yamaha and Adam Audio are both good and affordable. Many like the JBLs as long as you aren't too picky about hiss. Genelec is the very best and provably so by independent scientific measurement (see audiosciencereview.com measurements). But Genelec is stupid expensive, over $1k for a pair of their budget monitors. Anyway, this post is long enough and turning into an article. To summarize, get a Scarlett USB interface (~$160), the UMIK-1 ($99), a good pair of 5" or 7" studio monitors (Yamaha, Adam Audio, or maybe JBL, $300-$600 for the pair), and a graphic EQ. The bargain-basement Rockville REQ231 for ~$130 is essentially a cheap but good clone of a more expensive EQ. You can also spend $250-$400+ for Behringer or dbx/JBL which looks prettier in the rack but honestly doesn't sound any different.