proponents of matching the front three. However, I might be like you... willing to mismatch if that means having a better center. (I wouldnt want to "match" at the expense of having poor sibilant dialogue).
However, although there are a few audio buffs here, I would try a more audio-centric forum for experienced opinions (Ive never heard HK speakers).
If its possible, the best way, as always, is to try and see for yourself. Outside of that, it could be a gamble.
I have a Denon AVR-2105 receiver, with Harmon Kardon HKTS-14 speakers. Could someone tell me if I purchase a JBL EC-35 for my center channel, would I still get the voice matching and audio panning? I guess what I am asking is would it sound right?? Thanks...