What connections do you want? And budget?
Topping make very nice budget Chinese made headphone amps with great specs and able to drive the HD650. Like
https://www.amazon.com/gp/aw/d/B09HBS8SLJ I would run into that from S/PDIF. The audio specs/test measurements are so good it will beat a lot of pro-studio gear, but consumer focus construction/features, no balanced analog in, only 1/8” phono jack etc…. Topping may well be the killer bargain brand for what audio performance you get. But what features etc. do you want? We cannot guess.
Again personally I’d look for a used Grace m920. At ~$1k. My m920 gives me basic stereo monitor and headphone control and great multi-source switching S/PDIF from interface, analog balanced audio from elsewhere, USB from Mac etc. on a big fat easy to use source knob, and it has great headphone cross feed (without that I am not interested in any headphone amp). Super nice built box that sits right next to my keyboard. A heavy box, it does not slide around or get pulled off the desk by the headphone cables, unlike some small headphone amps. No power bricks just an IEC power cable, which I like. Lots of little things can make/or break any product like this for different users--mentioned some of my needs here just to give some things to think about. All depends on what you want.