Obviously this will be very subjective. If there would be an obvious answer, there would not be so many DACs and AMPs out there, would they?
I decided to go with new NAD 356BEE. I could get a used NAD c352 for ~200€, but having no warranty, and unknown usage conditions (theese A/AB class amps get HOT +15 years old...) might require recapping, which does not make sense as i found 356BEE on idealo.de for 388€ new, with 5 years warranty! (msrp 700-800€).
For DAC, I would recommend to go with latest stuff: newer DAC chips, aptx hd bluetooth support, optical input, etc. I went with this and so far I do not regret:
https://www.audiosciencereview.com/...of-topping-dx3pro-dac-and-headphone-amp.4967/
Total price for combo: ~190USD for DX3PRO + 388€ for NAD + shipping fees. Superb setup for the buck.