I don't really have anything to compare this to, since this is my first non-board soundcard (some might say I took quite a leap) To be honest, I wasn't even expecting that much of a difference on the price, since I'm used to seeing components paying way more, but the quality of the STX really blows me away! The headphone amp is something that could be better, my only other amp is a measly Pro-Ject headbox S, which performs pretty close to the xonar, although being slightly warmer and not as detailed, also I don't really like how it sounds on your general every day 32 ohm gaming headsets, or my 55 ohm akg k121's. The Xonar is a great sound processor though, in fact it's so detailed that it made me realize that I need a better speaker amplifier to keep up with it
 
TL;DR Great (value) DAC, decent head amp for 250ohm or above headphones