Will high SPL subwoofers damage planar speakers?

Audiooracle, Wrong. Innersounds and Sanders Sound can play that loud without distorting as long as the amp is up to the challenge. Martin Logan Summit's can play pretty loud as well but since I don't own them I'm not sure exactly how loud.

Quad's on the other hand will go into protection mode if played over about 95db. The sub would go louder though. I'm not sure how loud stacked Quads would go. Probably 3 to 6 db louder?

As far as the sub damaging the panels I doubt it. Many people have had Quads paired with subs before. Hopefully they can chime in.

"Quad's on the other hand will go into protection mode if played over about 95db."

The protection circuit is not saving Quads from damage.

sorry I beg to differ no electrostatic goes as loud as a dynamic speaker, the issue is the amount of air displacement and throw that the diaphram can move before it hits the stators.

The innersound are okay speakers at best, I have heard them on several instances didn't blow me away at the least.

At shows I heard a set of Vivid rattle out the lighting cans out of the ceiling, never heard an electrostat that could move enough air without getting hard at loud levels and compressing.

There is no perfect speaker. Some speakers excel at rattling light cans from the ceiling and other speakers excel at nuance and truth of timbre. They all have their place and everyone has different taste.