I talked to Zishan seller at taobao, and told him my preferred sound SIG(warm smooth in vocal), he recommended this upgrade - 49720HA X1+797 X2 +634XIIX2, plus "power/electrical(?) source alteration", I seriously have no idea what it would do to the device and what to expect.
I talked to the seller as well, he seems trustworthy, the above would certainly be a nice combo. I did try the 49720HA in LPF, it was the only other opamp I tried that rivaled the Muses01, but I couldn't get the pcb back in the case because LME49720HA is taller due to the TO-99 package, it would need some extra work to get it to fit. LME49720HA is overall warmer in bass, yet more forward in both detail and vocals while staying smooth and open sounding, compared to the Muses01 which is much smoother, more laid back in detail, tighter bass, not as forward in vocals with a thicker timbre to the mids, less open sounding, but not in a bad way, your trading open and forward for thick and dense, but one thing both opamps are is quick, the sound is never slow or even close to it. It's probably hard to understand exactly what I'm trying to say here. Both are about as good as opamps can get, with a select few others also in the top tier club like LME49990, AD797, AD8620/10, OPA627/37. Funnily enough all of them are offered by that seller, he has good taste that's for sure!
I also bought the accompanying amp, the GAD Mini A1, it is fantastic, adds an extra level of refinement and detail to the sound, more immersion, just an all round step up to an already great sounding dap. Highly recommended, it's a steal for $80, for sensitive iems you will have to turn off the "turbo" mode of the zishan dsd which lowers the output of the volume and line out, which allows sensitive iems to operate well with the GAD Mini A1, without any channel imbalance.