With $700-$900, I'd suggest looking at the Yamaha PSR-1000 or possibly a used PSR-2000. I too have heard so many negative things about the keybeds in the PK-7's... I played a PK-7 when I was in Florida some time ago, and I thought the keys were quite poor. Way too flimsy.

Squeak
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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.