At this point I would suggest waiting for the SR25 to be widely available before making any kind of purchase.
The SR15 is great and pretty versatile, it does streaming and sounds pretty great overall - though I guess the AK240 sounds better. Its biggest issue is that its battery is pretty measly. It's pretty much the #1 reason I'm looking for some alternative right now. And the SR25 reportedly has one of the best batteries out there... So if I was in your position, I'd either go for the 25 if you need streaming, or the AK240 if not (not sure about the 240's battery life, especially if you buy it used, though).
I use a fiio if I want to stream, so the player will just be doing local music playing. The battery doesn't really matter since a battery is already a part of my carrying gear, should probably wait for the SR25 to come out. Currently trading Koss esp-950 for 240 though, anyone interested?