Is there such a thing as audiophile parametric eq?

Yes, Rives Audio PARC it operates from 300 to 16 Hz in 3 bands and does a masterful job. I had similar issues and it worked.

My three Behringer DEQ2496 have functioned flawlessly for several years, and if one should fail I could replace it for less money than repair of the typical "audiophile" equipment. No doubt Behringer makes some items that are not designed to the audiophile market, but the DEQ2496 is not in that category. Again I say...get your hands on one and form your own opinion.

No doubt the PARC is great, although it has no RTA and lacks other features of the Behringer. Lexus cars are great too, but I drive a Honda.
.

The Behringer is a kick ass deal. You cannot hear any problem using the toslink to a dac. As a matter of fact I know a guy sold his dac and after he got the DEQ 2496.

Restock: I do not have a reference, though I imagine that somewhere in the Harmon reference white papers it's there--just a matter of getting through them all. It's pretty common knowledge amoung acousticians regarding the phase shift. As to the averaging and positioning, you are correct. We always recommend you work with speaker position and listening position before calibrating the EQ. You will find that once calibrated it's better and just about all locations, even if you calibrated for only one spot. We've done tests with averaging and usually get worse results because it's masks a portion of the problem. This is not intuitive and not what we originally predicted. It was literally hundreds of calibrations and testing that led us to this conclusion.

I have 6 Behringer units in saveral of my systems. Never had a problem with any of them.