I don't think it would be my choice, honestly. If I had the -IIa/b, and had to replace the EQ, I'd probably first explore the Marchand Bassis to see if it was desirable in this case. On the surface, I don't see why it wouldn't...an adjustable frequency with variable Q settings. You'd want something that brings the eq in where the frequency response of the woofers drops off because of the box response (essentially the Fc of the system and resultant Q). But, you have to start by knowing what that response is. Or, going a little further, what the complete in-room response is. The Loki offers a 20Hz center frequency for the bass region in question. That may or may not be an appropriate frequency for the system response. If one knew the possible response curves and variables of the original equalizer, that would be very instructive in searching for a suitable replacement. Because, you could assume that Infinity adjusted those response curves to be appropriate and logical to compensate for the speaker's in-box response, right?
In selecting a replacement, the astute would be cognizant of not only the final frequency response of the system with the eq in the loop, but also things like ensuring that the final eq curve does not cause the woofers to exceed their excursion limits at high power settings. If you tried to inappropriately eq the heck out of the very lowest frequencies, you may come up against this sort of limitation. Other considerations might include excessive voice coil heating (causing eventual failure, or at least a loss of damping) or generating a Q value that causes an excessively steep group delay curve at the lowest frequencies (contributing to a lack of coherency in the system). All this stuff is covered really well in the Loudspeaker Design Cookbook, by Vance Dickason.
I would bet dollars to donuts that I would end up with a DSP'd system that could implement the crossover between the EMIMs and the woofers (after removing the passive components), and then implement an appropriate eq in the bass region. The assistance of in-room mic readings using some of these units (like a dbx Driverack, for instance) that would then be used to generate selectable eq curves would be of great help. I'm not sure how many units are out there that have this capability now, but the number is getting pretty high. The Behringer DCX 2496 is pretty ubiquitous; I'm not sure if it has the mic capability or not, I'll have to look. I'm sure you could do it with some (or maybe all) of the DEQX units, if cost was no object.
It actually sounds like a pretty interesting project. Anyway, that's where my thought process would start.
G~
