Look, normally I would agree, but the Geshelli J2S encourages you to do so. They sell two sets of alternative op amps with the unit. I'm pretty sure that a pair of MUSES03 would be no more different to an OPA1656 than an SS3602 or Burson V6 is. The MUSES03 and the OPA1656 are both jfet. I've seen someone running MUSES01 and MUSES02 in the unit, so MUSES03 should also run, based on specs. Maybe there will be a slight increase in distortion, but nothing audible.
I've rolled op amps through an FX-Audio DAC-SQ5 in the past, and each time I heard some obvious change to the sound. Although in the end I ended up using the stock op amps, because they sounded the best, hahaha. Hoping things will be different this time.