I was reading the parent comment and just could feel myself itching to recommend AudioScienceReview, but then was glad to see it was already the top answer. It's such a relief when you finally have some hard data to compare options in that snakeoil-laden field.

I built my stack based on the reviews there, and I've been completely satisfied with my Topping D10 (for DAC) and JDS Atom (for an amp), which cost me like $200 total a few years ago. But of course, there's already a newer model of the Atom that seems to blow the old one out of the water: https://www.audiosciencereview.com/forum/index.php?threads/j...

And btw OP, for headphones I'm using DT1990s, which might also be worth a listen if you are looking to upgrade from the 990s :)