Anything new with digital room correction?

it robbed music of transients, dynamics and details were seriously affected.

I think you have to get used to it. If you have been living with room modes for a while then the presentation seems kind of exaggerated and you can get used to the larger than life presentation (like having lived with the contrast always jacked up all the way on a TV - either a note is very strong or it disappears in a deep null - very lively but unrealistic and lacking nuance)

I would not try to do much above 100 Hz in terms of adjustments and of course only on peaks. 100 Hz is 10 feet so a quarter wavelength is 2.5 feet and you are getting down to the sweetspot size.

Bear in mind you have to do room treatments first - as the nulls cannot be corrected for except by improving acoustics - so for sure it sounds dull if you have no bass traps even if you have EQ'd to remove modal peaks.

I agree about ringing of filtering can in general be a problem and fast digital filters with short taps are not always of highest quality and extreme settings can lead to ringing and phase problems.

FWIW I'd recommend only EQ the sub and don't aim for anything near perfect flat - just get the worst 10 or 15 db broad bumps reduced to a reasonable size (no more than +6 db and your ears/brain will handle the rest) and preferably don't try to EQ the main speakers - just in case you muck up the mid bass and lower midrange from digital filter ringing or phase issues. Remember that above 140 Hz you begin to hear directionally so I would not recommend mucking about with sharp (high Q) filters that may affect phase.

One advantage of digital filtering is the phase behaviour can be better controlled.

Sashav.

PMC used ATC midrange in the past. PMC are absolutely excellent speakers. I think they use Volts on the woofers but the design is similar to ATC but with more bass (TL design). If you already own PMC then I am not surprised you heard no reason to change. ATC probably have the edge with classical listeners and PMC probably has the edge with rock (more bass) but it is indeed a close call and at the end of the day a matter of taste. I'd probably be just as happy with PMC.

Humps are 50Hz on left channel and 40Hz and 70Hz on right channel, quite severe, somewhere around 8dB

That is actually not bad at all, IMHO. If you tried to hammer that all flat then I am not surprised that it might not pass for an improvement. Of course, the nulls are the worst....as certain bass notes just disappear.