Take a look at Woo Audio, extremely well thought of in the headphone world. Here's a link to Audio Advisor page https://www.audioadvisor.com/search-results/?q=woo+audio&page=2
The WA7 Fireflies $1,399 include a DAC and amp, while the WA6 $999 and WA6 SE $1,499 (Special Edition) are both amplifiers. I don't own them (though I've heard them with my headphones several times), but worth looking into.....and on my list when I upgrade my gear.