I was running Hifiman Deva Pro on my PC with a Soundblaster SC with a discrete headphone amp and it sounded ok. I don't have a huge budget so I bought a JDS Labs Atom DAC+ and Atom Amp+ and it sounds significantly better.

I have new Hifiman Deva Pro w/bluetooth that I hooked up to my Soundblaster sound card that has a discrete headphone amp. They sounded very flat and harsh and unable to get very loud. I bought the Atom DAC/AMP stack and they sound fantastic now. Definitely power hungry.