If you look at it the clear unrestricted free agents (as of now) who are the most interesting are Rondo, Marc Gasol, and Alderidge.
However with the money the Knicks have they could potentially steal Kevin Love, George Hibbert, or Kwahi Leonard by offering them a max money that they accept over their player option (in the case of Love and Hibbert) or their current team doesn't want to match them to a max because they are a great second player but not a player to build around (Leonard).
Those scenarios are far from sure things but if the knicks save enough room for 2015 even giving Melo a Kobe max they could still walk away with two of the players mentioned above and using bird rights still keep players such as shump, felton, and metta (if they aren't of course overpaid themselves) and JR would still be under contract.