Don, As much as the Bose shines when placed behind us ... I've found that it sometimes confuses the harmonizer at higher volumes. Now that you have the on board speakers ... try putting them even with your kb's front ... you'll hear from the PA900 speakers and there will be no bleed through. Shorter cables runs too! Just a thought.
_________________________
"Even the darkest night will end, and the sun will rise" ... Victor Hugo