Actually the MF02S sounds good using the GK80 it isn't as bad as I initially thought. Again more neutral in presentation. The funny thing is I know how the player supposed to sound it is more analoguish in presentation full bodied big expansive sound. But the GK80 sounds more neutral on it.
So I suppose if you want a more neutral presentation with less bass you gotta purposefully look for a higher output player.
I ordered one of those Dunu branded 30 ohm impedance plugs off AliExpress; ~ 17 euro iirc. There are other brands for less.
With that said, I regularly use the GK10 on a balanced cable led straight to my PowerDAC, which is about ~ 600 milliwatts at 16 ohms. There's some line level hiss but they sound great after the volume comes up.
Mine was defected (mid bass bloated). But after some hours try to mod them (clear vent holes, burn in, filter remove + foam mod) now they sound really good. I think you should try foam mod on this