Correct me if I'm wrong, but the PA -500 doesn't have a vocal mic input or harmonizer...probably more comparable to the PSR-S700 which, if the Korg price is correct at around $1500 USD, is again far less expensive, and has more polyphony.
Hard to find a direct comparison in either case.
Ian
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.