[Badsam]

Is there any preference as to which is better out of these two? I'd be listening exclusively to FLAC ripped from CD using a line out into a Fiio A5 connected to Sennheiser HD650's, no ESQ settings. I have no need for a DAC.

I've looked at the choices I have in the £150 range and these two seem like the only real choices I can easily get hold of.

 

[kimvictor]

X3II. Sony has their own thing going when it comes to DAPs. For some reason, all of their DAPs measure quite badly. They do sound unique and warm, so if you like that, give the Sonys a shot. But A15 was designed for decent quality in compact housing. If you're looking for a flat DAP that measures well and want to play it safe, get the X3II. The UI isn't nearly as good as Sonys, but if it's anything like the X3, it should sound decent.
 
That being said, I've only tried the X3 and the A15, not the X3II.

 

[kimvictor]

While I couldn't find measurements of the A15, the X3II measures better than the ZX2, which is supposed to be "higher end" than the A15. Of course, some people prefer Sony's sound, and I won't argue that. But if you want to play it safe, X3II.