Some synonyms for the word "more quintuple" include "five times more," "multiplied by five," and "increased by a factor of five." Another option is to use the prefix "quin-" to create new words, such as "quincentenary" for a 500-year anniversary or "quinquennial" for an event that occurs every five years. Alternately, you could use more general terms like "significantly increased" or "dramatically multiplied." Ultimately, the choice of synonym will depend on the context and style of your writing, as well as your personal preference for word choice and rhythm.