I agree with Don that you might have to wait a long time for the next models. However, if you wait one month (by which time the next NAMM will be over), you will at least find out whether or not it will be worth waiting for. (If, indeed, new models are introduced.) Whatever you get, you will eventually want more (I guess), so you might buy the 540 anyway, save money and get started earlier.
[This message has been edited by Clif Anderson (edited 12-23-2000).]