It depends on your budget and expectations. For example for a HD 650 a headphone amp is a welcome addition.
I use oppo pm-2 with ha-1 (dac and headphone amp) streaming Tidal.
It sounds really nice but it costed me close to 2 grands....
Dont know cause never tried youtube on it.
Be aware though, many high end headphones will reveal every shortcoming of the record so a ****** source will sound really bad.
Is it worth getting a DAC and Headphone Amp too ?
YouTube? Compressed beyond help,low resolution video,crappy sound.
I prefer to look up music videos (I guess it's those you're after,if sound quality matters) from Apple Music,generally better sound quality than YouTube.