I'm just curious why this list of "Resources for answering common questions" recommends the 1661 Tesoro de la lengua castellana o española for etymology? Is it still accurate, when historical linguistics has improved since 1661?
When researching etymology, it is useful to look at old sources to see how a word and its meaning have evolved over time. For example, if you want to know when a word started to be used in Spanish, a recent dictionary usually does not tell you that. Or if you know the origin of a word, but do not know why is current meaning is so different from its original meaning, such as in this question about why rodilla (knee) comes from Latin rota (wheel). So having both recent and old resources is useful for answering questions about etymology.
In addition, unless I am missing something, the two dictionaries you suggest do not provide the etymology of words. While they can be useful to answer some questions, I do not think they should be in the "etymology" section.