Hi GlynG:
I have tried two different 64 gig cards in my Aura HD and both work fine. Yes, fat32 is a must. In fact, all my devices have 64 gig cards, there was a sale on them a month ago!! The specific cards I use:
http://www.canadacomputers.com/produ...item_id=058667
http://www.canadacomputers.com/produ...item_id=057081
I am using the Adata uSD card in my AuraHD, but the sandisk works fine, but is way more expensive.
Best,
Shunter