Obviously a response 2 years later but if anyone is interested...
I heard from a knowledgeable dealer friend of mine that there were/are issues with the drivers going on the F50. He had 2 pair he took in trade and although neither of the those pairs had drivers that had failed he upgraded all 4 speakers to the F50A drivers just to be safe.
He felt he would end up taking the F50s back otherwise from clients when the drivers went and this way he's got F50As to sell.
I heard from a knowledgeable dealer friend of mine that there were/are issues with the drivers going on the F50. He had 2 pair he took in trade and although neither of the those pairs had drivers that had failed he upgraded all 4 speakers to the F50A drivers just to be safe.
He felt he would end up taking the F50s back otherwise from clients when the drivers went and this way he's got F50As to sell.