A total of 2 reviews of this product on Reddit.
I don’t think Fiio does anything portable and powerful enough that isn’t getting really expensive. There’s this Topping amp which claims it’s suitable for up to 300 Ohm headphones. Maybe that’s worth looking into. Some of the amazon reviews say they can push HD 6XXes which are 300 Ohms.
Whether you should go for the DT990s or the Meze 99s really depends what you would use them for, because they couldn’t be much more different.
> I feel they are plenty loud enough and the sound difference on the K712 between my setup and phone (pixel 3) is substantially different
When you say sound quality is there anything specific that stands out? Does it sound like things are rolled off, discomfort, or anything of that nature?
Assuming you want a simple DAC + AMP all in one this should fit the bill pretty well. If you want to go separates you could do JDS, topping, Schitt, and presumably others for around the $200 as well.
Review of the linked Topping with measurements