I own a Fiio X3 & i'm more than happy with it, but on Tuesday I will be getting a simfree Samsung Galaxy S5, know i keep hearing that the S5 is very good with music can play both FLAC & 24bit aswell, so be interesting to see how it stacks up against my Fiio X3 using my AT's-M50X headphones, my...

I think the X7 should use mSATA SSD drives, a 256GB drive can be had for around £90 these days, they small & both cheaper & probably faster than Micro SD cards.   The X7 could have somekind of slot for easy access to swap & add the drive.   I don't think anykind of DAP that out atm uses...