I have somewhat figured out that all 0 and 1 series uses the same driver and that it's more than than less the filters (black, grey, green) that are responsible for differences in sound presentation.
I have heard and owned a single driver PFE unit a while back and it was no doubt one of the best(better) single armature driver I have experienced with my preference of music!
Now, I wonder since you have experience with all the releases. Have you experienced that the upgrade from the single drive to the dual driver is really worth the around $400 more we will have pay for an additional driver and some R&D etc.
I know this a very triggy question and not so easy to answer. It's not meant to be, but I also feel that many more members are curious about this.