If you're leaning toward an arranger, be sure to give adequate consideration to the Pa4x. I personally like its more live/raw (for lack of better description) sound better, and think it's physical layout is more user friendly (both subjective impressions of course). If you're keeping the Motif, then I would imagine the Tyros/PSR sound palette would be closer in character to what you already have. That may be either more or less preferable to you, depending upon how you plan to use them, if you plan to use both together. I really wanted to get a Pa4x and came incredibly close, but then got pulled in a different direction when the Montage came out. I'm intrigued by the idea of some additional randomness and sound surprises resulting via the innovative sound/motion controls that come with the new architecture. That could be inspirational in its own way.