The 1000 is just an improvemnt on the PSR-640.. The 1000 only has 32 note poly no vocalizer, and many other options the 740 will give you.. The 1000 does however have an internal sequencer and now has more room for user styles too.. It also has a screen like that of the 9000.. Also keep in mind you'll lose the modulation wheel on the 1000 too.. Remember the 740 has 12mbs to the voices.. I'm not too sure the 1000 has that much.. I think Yamaha has a comparison chart on their site where you can compare the differnt models
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GEAR: Yamaha MOXF-6, Casio MZX-500, Roland Juno-Di, M-Audio Venom, Roland RS-70, Yamaha PSR S700, M-Audio Axiom Pro-61 (Midi Controller). SOFTWARE: Mixcraft-7, PowerTracks Pro Audio 2013, Beat Thang Virtual, Dimension Le.