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cypher is right in that こそ emphasizes the preceding word. However, the interpretation of emphasis is slightly off. It does not increase the degree of liking.

好きこそ means “liking, and liking only.” I think that in English, a similar meaning can be expressed using a cleft sentence: It is liking that makes mastery. (ものの[上手]{じょうず} is an archaic phrase which means a person who is very skilled at something.)

Using the first example in Paul Richter’s answer, 短い条文こそ奥が深い means “It is a short text in law that has a deep meaning.” It may or may not express the idea of “as much as.”