I agree that the Knicks have options, but I think Melo is, far and away, the best option. I also don't think it's that easy to play an uptempo style of offense in the playoffs. I don't have the numbers in front of me, but I believe that the better teams put more of a focus on defense in the playoffs, which slows the game down and creates a more half-court oriented game. I also think the better teams in the East will be able to put a focus on slowing down the Knicks, and not allowing them to get out in transition as frequently as they do in the regular season.
I also disagree that Melo doesn't provide anything other than scoring. He's averaging 8.2 rebounds this year, and has averaged 6.3 over his career. I'm also more impressed with Melo's defense than most. He's competent on the wings, and can provide help inside due to his strength, something the Knicks desperately need.
Furthermore, Melo fits in very well with this Knicks' offense. Unlike players such as Lebron, Wade, or Kobe, Anthony doesn't dominate the ball. He gets it, and makes his decision very quickly, whether that's to shoot, drive, or pass. This would mix well with Amar'e, and would not disrupt the fluidity that's so important in the Knicks' offense.