Multich stereo w/ combo electrostats & reg cones?

I love doing 11.2 multichannel stereo w/ my current system. I am using Infinity Kappa8 & Kappa7 for Front/Wide, Kappa6 for Sides, Kappa5 for Rear, small Kef's for Height, Kef Center & SVS PC13-Ultras for subs. I run an Onkyo TX-NR3010 to drive some speakers & NAD T975 to drive others. It sounds pretty good but I have been thinking about trying to change out my Fronts w/ a set Martin Logan's. Have any of you guys done something similar (mixing electrostats & cone speakers)? I am worried that the difference in presence/imaging would sound weird. Then again, maybe it would sound great?? Should I stick w/ just one technology? Should I plan a long-term conversion to all electrostats? I'd love some advice from those may have already gone through this :)

A multichannel system should have timbre matched speakers. Using all identical speakers is the absolute perfect timbre match. Subs do not need to be the same brand as the other speakers, but when using more than one, they should be the same, which you are doing. Your biggest problem is the Kappa fronts/wide and a Kef center. Going to ML fronts, Kappa wide, and Kef center will just compound the problem.
I use all Quad ESL's of the same generation. This provides a coherent sound, in which a 32Hz C clearly differs from a 36Hz B.

Not much bass below 30Hz, but everything above that is sublime, and that's 99% of the music. I suggest that you try it sometime - put a 12dB filter at 30Hz in front of a sub, disconnect the rest, and listen to the complete absence of signal, except for the occasional undifferentiated thump.

Every sub I have tried adds far more mud than signal, although I have hopes that, eventually, I can make my isobaric magnepans work out.