Another edition with a new control called Directionality, which kinda governs how much the speakers are toed in and spread. High values will turn the speakers almost into headphones. Zero is almost the old behavior with the inverse phase correction.

It's not really percent, but I forgot to change it to "exponent". I have to put an antilog there to make it linear.
This equation emulates the rotation of the speakers over a half-circle very well.

The mid and side equations are fixed to not "clip" - it was actually dropouts, not clipping.

Sounds much more like an incremental improvement over the previous one. Mainly much less 3-blob effect and no "barrel" sound on inverted phase tracks.

Dedicated to sucky mixes like this one: Megadeth - [Peace Sells...But Who's Buying? (Remastered) #11] Peace Sells (Randy Burns Mix)
And also good hard panned music like this: Clutch - [Jam Room #10] Release the Kraken

EDIT: Updated defaults.

A different setup simulating more of a near field monitor feel, would be like on the attached pic. Highly recommended, I'm considering switching the default to this.

The next "preset" simulates an anechoic chamber. Extremely analytic, but will work very well after adding some reverb. Also preserves almost all bass slam. (Updated cutoff frequency. Was too low, which made certain guitars fly off the scene.)

Comments: the anechoic preset sounds (spatially) like very near field speakers, not just anechoic chamber. Very similar spatially to my local desktop 70 W RMS Unitra Tonsil Space '86 non-bass reflex 3-ways, 60 degrees spread, 1.25m from center of head. In fact, has better subbass on these Sony MH1 IEMs (but worse highs).
That without eq; I don't have the eq curve on me for the modded version. They're not perfectly linear of course, just reasonably neutral with subbass boost.

The speakers start to roll at 60 Hz (-3 dB), but extension up is impeccable and neutrality is top notch, within 2 dB, no wide peaks or combing. Could be improved further by polyfill replacement and fixing the old suspension, which worsens bass THD somewhat I bet. Very fast and controlled sound, like many closed box designs.
They look like this: http://archiwumallegro.pl/unikat_czarne_unitra_tonsil_space_86_oryginal-1023345693.html

Superb polyamide tweeters. Mids are good, bass is decent. My pair doesn't have the domes damaged, but instead the woofer suspension got worn. HDF front, plywood sides, thick LDF back. Woven fabric low density fill inside. Mine were also extra hot glue sealed.
Front cover is and rolls off the extension up - it is also rather unnecessary, unless you have small kids around. I've been guilty of putting my fingers once or twice into the domes - they're stiff polyamide foil. Mids and bass are heavily processed lacquered cellulose.

Crossover is 2nd order Butterworth symmetric, not sure about frequencies. As this is a late, improved cross model, I'd bet on 1.5k and 4.5k crosses. (If not, I'd fix them to this.)

Bass: Tonsil GDN 20/40/14
http://www.e-tonsil.pl/index.php?p45,gdn-20-40-14
Mids: Tonsil GDM 10/60/4
http://www.e-tonsil.pl/index.php?p63,gdm-10-60-4
Highs: Tonsil GDWK 7/50/19
http://www.e-tonsil.pl/index.php?p76,gdwk-7-50-19

All are still being made by Tonsil and used now in "mid-range" low power stage monitors.

so what is the best version with the most realistic sounding default setting that i can try right now? Can you give us a link?

A suggestion for an added feature:

Could you add a left/right toggle?
You could turn off the right channel so the left is isolated for crossfeed proccesing for easier tweaking.
That way you could tweak the "left speaker" emulated and compare with a real left speaker easily.

Tried the latest adv_xfeed_v3. Excellent work. Best crossfeed plug I've heard, but is there any way of editing the default parameters before it loads? I use the VST adapter for foobar and it loads and applies your plugin, but cant display a GUI.