HELP - buzzing on Magnepan 3.6R; repair or not?

I was trying to sell my Magnepan 3.6R's which I purchased used from work (along with a pair of ML Odyssey's which I decided to keep. I was demoing them to a prospective buyer last night. I was playing deejay and threw on about 7 or 8 different tracks - chamber music, jazz, orchestral, pop vocal, etc.

I find them bright in my system so I wanted to make sure the prospective buyer understood that so I played a track that demonstrated that explained that to them. I said I didn't know how they rocked though so offered to put something on. I grabbed a White Stripes CD which has some extended bass notes on it. One of the panels started to vibrate/buzz. ARGH! Of course, I didn't know that when I bought them, but I received a decent enough deal from work that I can't complain.

So, I have two avenues I can pursue to sell them - one, sell as is at a steep discount (the prospective buyer is actually still interested in this as an option since he has no other components for his system yet so can wait) or two, repair them myself which would then allow me to market them as having a new panel and at that point I'd also now have boxes to go along with them. Which avenue of sale makes the most sense?

I left a voicemail at Martin Logan service early this morning (8:30AM their time), but did not receive a call back. Does anyone have any idea what it costs to repair this? I'm assuming this is not something that can be field repaired by me.