Ifill had another chance nine minutes into the second half but he walloped high. Then, on the hour, came Brown's gem.
Reddy cleared towards halfway. Nicky Carle met the ball on the fly and, on the edge of the centre circle, dropped it down, harmlessly, it seemed.
Brown swooped and, spotting Reddy a little off his line, launched a 40m effort, as much in hope as conviction, and then watched in delight as it dipped over Reddy and into the goal. Stung, the visitors picked up the tempo.
For 20 minutes they asked the occasional question of the well-organised Phoenix defence but with the central pairing of Ben Sigmund and captain Andrew Durante at their best they were rarely tested.
Then, out of nothing, the Blues were back in it.
As the ball harmlessly bobbled about, substitute Bruno Cazarine stuck out a foot, found it hitting the ball and watched as it slowly rolled away from goalkeeper Tony Warner over the line.
Durante and Muscat (for the fifth time this season and facing an automatic one-match suspension) were booked as Sydney poured forward but, after successive home losses, the Phoenix dared not contemplate a third and held firm.
In celebrating their return to winning form, Ifill was still shaking his head in wonderment at Brown's goal.
"I wondered what he was doing," said Ifill. "Then I saw Liam's face and knew he was beaten."
Brown was understandably happy with his effort. "You get a bit of stick when you try something like that and it doesn't come off."
Coach Ricki Herbert described the win as convincing and said he was delighted for the players.
"We've been playing well in most games without perhaps getting the results we deserved," said Herbert. "It was good to get Paul [Ifill] back because he is massive for us and capable of changing a game. You could see how pleased he was to be back out there after his time out ...
"Sydney is always a good scalp to get and while we made it more difficult than it should have been by conceding the late goal, we got there."
They will now take that confidence into Sunday's game with Melbourne Heart in Morwell.