So~, I recently bought a FiiO BTR5... For those unfamiliar, it's basically a miniature Bluetooth-connected DAC-amp. It pushes a pretty stout 250 Watts, according to the product sheet, though word is it can go to 300W, and drive an HD600.
I have to say, for once, it really does live up to the hype. The battery lasts for two days powering my WH-1000XM3's, and it offers a full range of Bluetooth protocols to sync with your phone, though a USB C>C or A>C cable makes it great for laptops. I hooked it to my laptop running the latest Pop!_OS, and it works flawlessly.
I will say the Sabre DAC in the device has a slightly different sound character to the Burr-Browns in my iFi equipment~... Less laidback, and less warm. One instance stands out to me, when I noticed crisp cymbals in a live recording, wherein they were muted before. It's possible this was just a problem with my EQ curves, so this is just a curiosity. ^^'7
I also bought a pair of DT 770 Pros, the 250 Ohm versions... I'm still playing with EQ presets on them, so I'll get back to y'all on them. ✨