Those are good points, but unless we want to say Paul has contradicted himself, we have to make a conclusion somehow.
I conclude the following:
When Paul wrote "the spirits of the prophets are subject to the prophets", he did not include any definite article before the word for prophets, or for spirits, meaning no "the" is anywhere present in Greek.
See:
http://biblehub.com/interlinear/1_corinthians/14-32.htm
This means that Paul is not referring to the group of people who should be understood as "the prophets" as in the five-fold ministry. Rather, he is merely referring to those who prophesy under the unction of the Holy Spirit through the gift of prophecy. This doesn't make them official prophets in terms of the five-fold ministry. Rather, that when one prophesies, one is temporarily gifted to function like a prophet.
Was King Saul a prophet? He prophesied, but he is never called a prophet just for doing so. Caiaphas prophesied, but was not a prophet.