If you use your IER-Z1R on the go, do yourself a favor and but the Fiio BTR5 Bluetooth receiver, a Fiio LC-2.5C Balanced 2.5mm MMCX Cable and pair over LDAC with your Android phone. All up, about $195 USD. Will you get the most detail and refinement out of your Z1Rs with this? Absolutely not, but the convenience outweighs the drop in sound quality IMO. You will always get the best sound at home using a desktop DAC of course, but the BTR5 & 2.5 mm cable combo is great for the price, sturdy and cheap enough to replace if something goes wrong. You can drop the damn thing but it is so light it doesn't matter. That $2k DAP on the other hand... Add to that the current trend of phones ditching audio ports and you see why the mobile hi-fi future is wireless. LDAC is pretty damn good, maxing out Spotify's streams with ease, and there is even better wireless streaming tech in the works. Don't even get me started on how well Nvidia Shield Pro TV sound over LDAC with my IEMs and cans, that's not on topic...
I'll go now for a walk with my new gonzo BT setup