While I understand the sentiment; it's not a currently produced unit; and that's why it's not on the list.
The HX850 is better in some performance regards to the AX850 slide efficiency; so if it was still produced it would be on the list. But it is not.
The list is meant to stay as up to date as possible on current PSU's.
I'm just thinking out loud now, but maybe it is possible to make a list of PSU that arrent 'new' but still are good enough to be recommended? Or whould this be very small list and seem useless?
Anyway, the point i am trying to make is that it whould be fair to mention the HX series. They are still available on a lot of sellers, cheaper and just as good!
If you disagree, i'll won't be a ***** about it ofcourse