[dc-k]

On their official site, it is said, that it supports up to 256gb sd and 128gb microsd. That makes total 448 (with internal storage)

AK claim a max of 128gb per micro sd for the titan but it has no trouble with 200gb per slot. 

 

[ThinWalls]

Flash modded iPod Classic/Video?  with 2x512gb sdxc or 4x256gb micro-sd.  Or is that kind-of cheating?

 

[dc-k]

  Flash modded iPod Classic/Video?  with 2x512gb sdxc or 4x256gb micro-sd.  Or is that kind-of cheating?

I say kind of cheating but it's a free country
 
See also USB on the go which could take storage on some genuine DAPs comfortably into terabyte territory

 

[raulromanjr]

My Samsung Note 4 has a 512GB SD PNY Card and 20GB of available internal storage.