Room correction - what device works best?

As far as I can tell, I have used all of the devices so far mentioned (as well as some others) and, honestly, they all work. The variables are:
1. Bass only or full range.
2. Analog only, analog in/out DSP or digital in/out DSP
3. Automatic implementation of filters from measurements or independent measurement and implementation (more hands on).
4. Single measurement point or multiple measurement points.
5. Single pass listening area measurement/correction or separate near-field correction followed by room correction.
6. Fixed or variable target curves.
7. Stereo or multichannel.
8. Hardware or software.

What device works best? Depends on your choices and your room acoustics.

I grew interested in acoustics and having a technical background and DIY inclinations, studied quite a bit, got a measurement mic, mic amp, REW software, and built a number of tube traps, Helmholtz resomators, etc. also worked a fair bit on layout. The benefit was very apparent, although my wife wasn't as happy with the ugly stuff in the living room. But proved room treatments are worth the effort.

My only source these days is a very optimized PC with hardware and software optimizations, feeding an Audiophilleo and Metrum Octave DAC, a Lamm LL2 pre, a McIntosh Mc275 amp, 3-way speakers and a pair of subs.

Recently I incorporated Acourate software. Along the lines of Dirac, but less automatic and more powerful. So far I have been using it for room correction only and it works wonderfully. Miles' Tutu playing now, sounding as real as ever before in my system. Imaging has improved a lot.

I guess purist is in the eye of the beholder. My purist plan is to go fully active 4-ways and enable Acourate ability to run digital crossovers, driver linearization, and time-alignment. An amp driving directly a speaker driver is as purist as it gets in my view.

A couple of good articles for those who might be interested in learning more, at computeraudiophile.com, by Mitchco:
Introduction to Acourate: explains the basics for a 2-channel system. What I'm doing.
Advanced Acourate: explains how he implemented his 3-way active system, linearized drivers, time-aligned.

"Many audiophiles are "purists" at heart, and as such are closed-minded to anything that does not fit their purist mindset. In the case of room acoustics and EQ keep in mind that most of the people giving advise have little or no experience working with electronic EQ. Even if they have tried electronic room equalization, there is a learning curve and they may have given up before they fully understood how to use their device effectively. That said, it's not exactly rocket science."

I would probably be classified as a purist. At least by your standards. I think you mean purist to be someone doesn't have the same opinion as you.

Lets say that you removed your stereo system from your listening room and put a piano in its place. Like most rooms, its not perfect, so for this example, lets say the room excites a range of frequencies in the upper mids. Those notes sound a little louder than the others due to room acoustics. How would you fix the problem? One way would be to open up the piano and modify it by putting more felt on the hammers to the keys in the problem frequencies. Now all of the notes have the same volume if you hit them with the exact same amount of force. A flat frequency response. Another option would be to just leave everything as is and just live with the problem if its not too bad. And finally, you can fool with the room and not the piano. As a purist, I would go with one of the two latter options. Given the components the OP has, I believe you would do more damage to the systems sound using processing, digital or analog, than choosing another option.

Some may argue that this is just my opinion. That's correct, it is. But I do base my opinion on actual experience, and not just guessing. I have a Behringer 24/96 digital EQ that destroys the sound of my Wadia CD player. I also have a dbx analog EQ that ruins the sound of whatever preamp it gets used with. So, in my opinion, the OP's Ayon CD player is just to nice a player to be run through processing.

One option to consider is if you live near a Guitar Center, they stock the processors I mention, and many more. They have a great return policy so if you try something and it doesn't work out, just return it.

I did my research and I was willing to invest the time and money. I went with DEQX. No regrets.