I think you're confusing the matter needlessly. If you look at Amaryllis by genus, you will find only two species.
http://garden.org/plants/brows...
The other genera are included in this list because some Amaryllis species were reclassified as species of Rhodophiala, Hippeastrum, etc. These species are included in those entries as synonyms, and that's why they show up on the Amaryllis "browsing by genus" list.
If you look at the Amaryllis database, on the other hand, you'll find that it is already an "alliance." All of the Amaryllis and Hippeastrum species and cultivars are listed there.
http://garden.org/plants/brows...
Amaryllis is added to the entries for Hippeastrum species and cultivars because it is their common name.
