Everything that will make the K712 produce music already has a DAC and an AMP in it, including your "Z" card. It's not difficult to make such a device do a good or even great job and you will quickly encounter the point of diminishing returns buying anything "real". Something else might sound a tiny bit different in some way but in essence, if what you have goes loud enough for your hearing preferences and you don't hear anything obviously nasty in the combination (usually distortion), you are likely not to find *much* improvement by going with something else.
I have to disagree with your statement. My experience with both the Q701 and K712 has been they scale up or down according to the audio chain. Now I'm not saying you have to sell a kidney to get the K712 to sound good but i am saying not all amps/DACs will cut the mustard when the K712 is involved. For example, I find the K712 to sound rather great on the Schiit Vali while sounding pretty terrible on the ALO RX MKIII-B, sounded to brittle for my liking. Some other good/decent pairings, on the Play It by Ear amp it sounds pretty good and on the Ember its a hit and miss situation based on tweaking the amp with tubes and output impedance. If you have the patience to experiment it can sound pretty good. Personally I liked the K712 on the ember with the impedance set on its second setting while utilizing a RCA tube. On the iFi iCAN, really didn't like that pairing to much, the mids sounded kind of bleh to me and the bass sounded rather loose.
Just my two cents of coarse, carry on.
Edited by DigitalFreak - 3/29/15 at 2:34am