have a look through here for some starting info. https://www.reddit.com/r/Zeos/comments/66xylk/guide_dac_amp_combo_units/ & https://www.reddit.com/r/Zeos/
personally I would say be careful i have been looking for an amp/dac combo and have recently looked at this make, sold primarily on amazon. Very few reviews seems to me to be cheap Japanese sweatshop imports. I even e-mailed them to ask them about an amp i was looking at to Which there was (no reply) good sign for customer service eh😊. As for driving 650 ohms headphones i think you'll have to find something a bit meaty. I have the Beyer t1 second gen and use the audiolab m-dac first gen which I found cheap but people swear by the schiit (lol) or little dot.
I have a beyerdynamic 🎧 650 ohms is that OK thanks
Consider that your monitors likely have built in amps why do you want to amplify the signal to them, all you want to do is send a signal to them. Next this is designed for headphones which have a different impedance rating. So use the right tool for the job and you are less likely to damage any of you equipment. The items I listed are designed for their intended purpose, whilst the item in the post is designed for the use with headphones.
I recommend a steel series 5H v2 such as m.ebay.co.uk/itm/Steel-Series-5Hv2-Virtual-7-1-Channel-External-USB-2-0-Sound-Card-Audio-Adapter/231771365495 Which does have very very impressive sound. and drives higher Impedances like a champ. This would be my solid midrange recommendation but I would say beware the cheap fakes. But again compared to the LG G5 DAC for around 15-20 quid.. that has to be my recommendation if you have decent earphones/headphones.