Is there really no difference in sound?

[ZolaIII]

There are differences between amplifiers; cheap class D and older ones in general will have smaller damping factor and be load dependent. Other than that cheap class D will have rising noise and distortion with frequency resulting in self hiss which can be very annoying and you hear it all right when not playing anything. Better autended not so cheap class D or H one's won't have any of those and will be very quiet and so will very good class AB and H ones with only little worse regarding measurements then SoM based modern ones. Then there is a difference in reliability and longevity but that one is more based on prowen and trustworthy brands which use quality components and don't skimp on power converters either regarding strength or quality (iron core, triodals). Of course all of those cost including prolonged warenty and spare parts availability guarantee. The tubes color the sound by having pronounced second harmonics. They don't perform very good they can perform good enough or even very good when used only as stage oscilator without almost any gain added.
E1DA as you didn't really mention which I guess current gen balanced only is for headphones with such instalation or modified to it. Most headphones are unbalanced including all you mentioned.
iBasso had some charming CS43131 implementations but DC03Pro ain't one of those. Actually I think that one is problematic regarding used USB bridge and they never sort it out for it. They did with later ones (probably by switching to another one) and those are more expensive. DC03Pro is unbalanced and impedance sencing limited; it gives full 2 V on detected impedance over 150 Ohms or so and does - 3 dB reduction for those under. So neither is really what you want. I will ask what exactly is that you want and for which price?