The phrase "most top echelon" can be replaced with a number of synonyms depending on the context and intended meaning. Some potential options include "uppermost tier," "highest levels," "elite ranks," "cream of the crop," "top tier," "upper crust," "high society," "upper echelons," and "the very best." Each of these phrases conveys a sense of exclusivity, prestige, and superiority, highlighting the idea that something or someone is among the most elite or esteemed in a given field or category. Choosing the right synonym depends on the tone and context of the sentence, as well as the emphasis and intended impact on the reader.