Quest, Quest-Z, ReQuest, ReQuest II,???

Can anyone help with the timeline and differences between
the Martin Logan Quest, Quest-Z, ReQuest and the ReQuest II?
Any thoughts as to the most and least desirable of the
I have heard the Quest, Quest-Z, and Request. I don't think I've heard the ReQuest II. I don't know the timeline on these. The Quest and Quest-Z sounded very similar. The biggest difference was an increase to the overall impedance of the speaker so that it wouldn't be so difficult to drive. The Requests sounded considerably better. The bass was better (tighter and deeper) and was also better integrated with the panel. They did make some panel changes, but that really shouldn't matter, because most Quest and Quest Zs will have had their panels changed a few times by now anyway.
The Request two was simply revamped speaker connectors and upgraded ETC spikes. The speaker was identical to the Request!!
I bought Quest Z's new a long while back, very happy with them. Why would the panels need changing? Do the panels tend to fail and need replacing?