The first thing to test is whether your sound card (onboard) can play 192khz.
To test it right click the speaker in your task bar. Go to playback devices. Right click on your sound device and go to properties.Click the advanced tab. Set it to 24 bit 192000Hz (Studio quality).
Click test. If it plays sound then you don't really need a sound card, you just want a headphone amp.
Most onboard sound cards these days can do pretty much everything a high end sound card does. However, sound cards do have better amplification circuitry however that's no valid reason to buy one. I would much rather have a good headphone amp driving my headphones than just the sound card alone.
I have tried various headphone amps and ended up settling on two of the best. One for pre amp, one for power amp. I loved the honesty of the Graham Slee Novo Entheos, but I loved the warmth of the Little Dot MKII. However, the LD was not powerful enough to drive my planar magnetic headphones, so I just use it to shape the sound before it goes into the GS.
However, during my time testing I bought a Little Dot MK1, link here -
https://www.amazon.co.uk/Little-Dot...TF8&qid=1480546928&sr=8-2&keywords=little+dot
It's not full valve, so is far more powerful than the MK2. However, the sound is absolutely the best I have heard from an amp costing that much. Sadly mine had a bad solder point in the valve holder so had to go back. I decided to go with the MK2 instead.