Denon has models with similar and better features, but I don't think for any less. Generally when you pay less, you get less.
One thing to think about: Mike Up pointed out in a recent thread that the 5590 lacks pre-outs, and he said that no other receiver in the $800 price range lacked that feature. He then pointed out that Crutchfield was no longer selling that model, perhaps for that reason. With that in mind, you might be able to get a lower price from any other authorized outlets that aren't going to carry it any longer.
You can also get new ones on auction sites for close to $500. Not sure what happens w/ the warranty under those circumstances though.