DonM is quite right but you have to ask which of the feature are useful to you.

I was using a PSR2000.

I upgraded to a PSR3000 because I couldn't justify the further expense to a Tyros 1; the sounds on the 3k are very good.

The main driver for the upgrade was the use of a Smartcard rather than the floppy drive; the ability to use USB storage as well as the quality of the sound confirmed the deal.

If my 3k was crushed under a lorry I'd by another one.

Since the 3k came out they've unleashed the Tyros 2. I've seen a demo and played the beast 2 and consider it to be a considerable improvement on the Tyros 1. If I was given some money by an unknown relative I'd be extremely tempted to buy a T2, and I couldn't say that about the Tyros 1!