I had a Yamaha PSR630

First I upgraded to a 2000. The main reasons for upgrade then were ease of use, improved floppy disc handling, more polyphony, better sounds.

Then I got a 3000. Main reason elimination of floppy disc altogether and the availability of USB devices to expand further if necessary. The better sounds and greater polyphony also helped in the decision.

Should the 3k become unserviceable I'd buy another unless by some miracle I could afford a T2.