I own a Zishan Z2 en Z3. I have changed the Opamp for a more lively one and last week I put in a 2600 mAh battery. I have now 10 hours of FLAC and DSD music on a 200 GB Micro SD. I love the Zishan Z3. I use it neutral with no changes in the EQ. I don't understand why you would change the EQ, because it always effects the musicsignal! Fase shifting you know! When you want more bass, then buy a Beats or an other bass-loaded pair of cans. Need more high? Buy a pair of Grado's. I use my Zishan Z3 with the Koss Porta Pro. It's a great set for less than € 100. Not flashy, but I am not flashy. I want good sounding music. An other Opamp also does a lot.
I sold my Fiio X3 because the Z3 simply sounds better and it doesn't cost ages to update the contents of a 200 GB-card when you make changes in the content. It is superfast and simple. I have also sold my Hidisz AP60 which sounded dull and use was horrible. For about € 35 you get with the Z3 a lot of music pleasure. The other Opamp costs about € 3,50 from China and then you have two (also for my Z2 whish I use as DAC for my laptop. The 2600 mAh battery costs about € 12 from China and soldering is simple and now I have music allday.

Update 9 may 2019
I fitted my Z3 in january with the bigger 2600 mAh battery that just fits, but now after using it a while I have problems with readind the SD-card. The Z3 stops, starts up again and refuses to play certain tracks. I opened up het Z3 and I saw that the sd card slot was damaged by the battery and the sd-cardslot damaged the battery. Earlier I examined that the SD-card had trouble to get out of the slot, so the bigger battery is good for long power, but it destroyed my sd-card slot so reading my sd-card is a now a problem. There is also white stuff on de sd-card slot from the battery. It looks as if the sd-card slot was pushed up together with the usb-slot by the thick battery. Maybe chosing a slimmer battery is a better option, when you want to extend batterylife.

Update 13 August 2019
I had to remove the 2600 mAh battery from my Z3. De battery expanded and was damaged by de SD-card sleeve. When I opended the Z3 the back lifted itself a bit after unscrewing only one screw. There was pressure inside and I want to warn you that with the damage I had you possibly may wait for explosion of the battery. I hope that it will not be in your pocket at that time. I removed the battery and put the 1500 mAh-version back.

I got the F.Audio S1 yesterday. Today I tried in my 200GB microSD fully filled with music, but het F.Audio could not read it. Out of the S1 I put it back in my Zishad Z3 and he could not file the music op de card anymore. All is gone.
Later I tried a 64 GB card filled with music and I found the same problem. The S1 could not see the music op the card and back in my Z3: Gone was my music.
So be careful and don't put filled cards of 64 GB and larger in de S1 because you wil loose your music.

Further disappointment in comparisson with the Z3 is that shuffle play is only possible within the folder and not through all folders. For me this is an great disappointment and the reason I sold my Hidisz AP60.

Conclusion: For the money you better buy the Zishan Z3. It's cheaper, can do a lot more, can play 200 GB cards and does shuffle through all the folders, and an other big plus is the speed of the Z3. I sold my FiiO X3 first edition because reading a 200 GB card took ages. The Z3 has the menu within a few seconds. Really!