Dnj,
I agree with you on the EQ setting. I don't have the PSR-9000, but I do have a Casio MZ-2000 and it has a master EQ as well, plus you can really go deep into the settings to bring the board alive. Most boards that have master EQ's, their default settings are generally lower and a little muffled. This was the problem with my MZ. After making some alterations it really brought the board to life.
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.