finally my old headphone is broken after many years.

So I have to buy a new one. A better one !
I need it for mixing and composing at my PC.
A often found "sweet spot" recommendation: Beyerdynamic DT990 Pro ?
But, a good headphone means you need a goode A/D device, too, which is not delivered by my PC (simple realtek chip onboard).
Do I need an audio interface then, or an extra headphone-amplifyer?
Which audiointerface has good sound (simple one for beginners)?
thanx for any recommendation! (headphone + USB-soundcard/interface)
