The more I hear about what you want to do---the more I still say the WK-3000 or 3500 will work for you. I don't know if you remember or not, but the new WK's have an SMF player. You can load tons of SMF's into the board say prior to a performance, and call them up very quickly. Plus the SMF's are stored in memory even if the power chord is disconnected from the board. For $450 you could get a WK-3500... They sell for $399 here in the US.

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.