The ASUS Xonar Essence STX has an astonishingly good headphone amp in fact this is the reason why this card purchased in 2013 remains in my PC. What is magical about this SC is they make your over the ear cans disappear off of your head. What you are hearing sounds like it is coming from your speakers, you cannot “hear” the headphones it is a 3D sound I have not heard anyplace else. This is not a simulated surround sound this is a straight stereo output. I keep having to lift one of the earphones off of an ear to confirm I am not blasting the room with mind bending volume, and believe me I have a 1500 watt 5.1 system that can cause earth quakes. I am listening with AKG 240 MkII’s.
A really nifty thing about the Xonar Essence is it has 1/4” phone and mic jacks.