aaaand uhhh AFIK Eden Black is not even available in the US....if it is, it is in very few, limited collections and would not be that size as the ones that have been released over the last year or so have been very small plants, and those were in europe where the source lives...
Why would you jump into this many rare, ceph clones if you are having problems with your hummer?
i would have at least waited until that one rebounded to ensure that you can grow them...
if that is indeed a true Eden Black, and that thing croaks, i can imagine not only will your wallet hurt, but many cephalotus enthusiasts in the hobby that have been on the waiting list for quite some time for one of those.
As far as your comment on "previously undiscovered form"
it is not a form, it is an unregistered cultivar.
There is one one species of cephalotus, and any cultivar/color variants under it, but no listed varieties or subspecies.
i really hope you know what you are doing, because just buying them up and putting them into an uncertain set of conditions, with what has already proven negative results, could be quite devastating to your collection and again, your money.
when you say reasonable prices, that makes me think even more that the Eden is not the real deal, because one could fetch major money for one of those, much more than a seedling N. edwardsiana would bring in, and one of that size were it the real deal, would probably amount to the price of a near mature specimen of edwardsiana, that is just how rare that clone is.