I would say that calling the Egyptian state religion monaltrous is a far stretch at best. Whilst some cults focused on one particular God, whom they revered as 'greater' than the other Gods, I do not believe that the entire pantheon could be viewed as mere 'reflections' of this God. The most amusing take on this has to be the view of some modern Egyptian Religious re-enactment groups, who base their entirely henotheistic religion on the occasional use of the word 'netjer' (sing.) in prayers of adoration to mean that the entire pantheon is part of a greater God, as in Hinduism. Even the cults of Aten and Atum cannot truly be called monaltrous, and using the whole 'netjer' thing to try to support this argument is certainly ridiculous.

I do not believe that there is strong evidence to suggest Henotheism in Egypt at any time other than during the reign of Akhenaten.