Nigel,
Buy the 2000/2001 and you'll never look back--there's a huge difference between the 2000/2001 and the 550. As for the key feel, hey, it's not a piano--it's a synth--two different instruments. If you really want it to feel like a piano, slip a strip of foam rubber beneath the keys. I did that to a friend's keyboard and he raved about the great key feel. He was an accomplished piano player. The sweet sounds, incredible guitars, excellent piano and all the other features make the 2000/01 the best keyboard on the market for the money.

Cheers,

Gary