This adapter:
http://dx.com/p/sd-to-microsd-transflash-card-converter-module-27001
works with this card:
http://patriotmemory.com/product/indexp.jsp?source=4&catid=88,90,89&src=4,7#product_line
Formatted at FAT32 on a Mac using Disk Utility. I had already been using it in a Samsung S4 that I dedicated to DAP duty. No reformatting was necessary. It scanned the whole file structure (about 110 gigs).
I had to rig up a little makeshift covering for it, but it works perfectly. There are other SD-MicroSD adapters out there, but this is the only one I've seen that's on a ribbon cable. Makes a big difference.
I'm sure that when 128 micro cards come out they'll work, too.
That said the X3 is going back to the store. The UI makes the AK100 look like an F-22. The fact that I can't browse by Artist to Album tags is unacceptable. I re-did ALL of my tags last year so I know they're clean. Also, to not have a way to fast shuttle from A-Z and in between is interesting in 2013. Even the Ak100 had that advanced feature. In my completely uninformed opinion, these annoyances are writing checks that the sound quality can't cash.
Anyway, in reading this thread I hadn't seen anyone actually try this configuration. To be honest, seeing if it would work was one of the top two reasons I bought the thing.
John