Synthmeister,
If you are considering the Ketron SD-1 or KN6500 besides the PA80 you might want to explore some further options. Have you considered the Yamaha Tyros or the KN7000? Both of these boards have outstanding sounds plus they have more Polyphony. The SD-1, PA80 and KN6500 have 64 note polyphony while the Tyros and KN7000 have 128 note polyphony. If you find yourself doing complicated arrangements, with many layered sounds and Pads you may find yourself running out of polyphony when using a 64 note polyphony arranger. You would have a lot more "breathing" room when using a 128 note polyphony arranger.
PS: The reason I am mentioning the Tyros and KN7000 is because you said you were considering the SD-1 which costs around $3,000. Also the SD-1 and Tyros have NO inboard speakers so if you want a 'grab and go' board the KN7000 DOES have built-in speakers. Note: The Tyros does have optional external speakers that hook up to the keyboard but that's an extra expense and also makes it "less" portable. But the Tyros does weigh less than the KN7000.

Best regards,
Mike