Magee set up the game's first goal by Juan Luis Anangono in the 25th minute, then added a tally of his own in the 42nd.
Jalil Anibaba supplied what turned out to the game-winner with a score from 21 yards out in the 52nd minute for a 3-0 lead.
With the result, the Fire (13-12-7) moved into the fifth and final playoff spot in the Eastern Conference.
Kenny Cooper notched a pair of late goals for Dallas (10-11-11), which was officially eliminated from post-season contention.
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