I did a similar thing with the arranger keyboards! Here was my path...

Yamaha PSR-3000
Yamaha Tyros 2
Yamaha PSR-S900
Roland BK-9
Korg Pa900
Yamaha PSR-S970
Korg Pa4X-61

Great expressive sounds... full sequencer... MP3 playback... great build and size. Every keyboard has it's strengths! Do your research and you'll be happy!
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~Johnathan
"The Shueys"
www.shueymusic.com
Yamaha Genos - RCF M20x - RCF HD10A (Stereo) - Jupiter Pocket Trumpet - Sennheiser e935 - Neumann KMS-104 plus-N