I have owned a Creative, Asus and Auzentech sound card and none of them had any fidelity at all. the designs are so old. drivers are a pain in the ass. PCI express cards have way too many space, weight and power limitations. you can only do so much with a PCI express card. Asus was on the right track with the Essence One but it's poorly executed.
Xonar DG is a great little card for what it is but if you want fidelity you have to think outside the box.. literally.
AS long as its not a crazy 800 dollar sound card, any Asus product will work, even if its 2 or 300 bucks.
If you only play indy games and LoL, I suggest you get a DAC which will sound much better musically. The problem with that is, unless you purchase a DAC/Amp combo unit, you will have to purchase a separate amp. An Asus DG sound card will come with an amp, but the music will not sound as good as if you were using a DAC. Ultimately it is up to you to decide, do you just want amplification and don't really care about audio quality or did you want your music to sound much better (restrictions apply)?
$198. You will need a couple of small RCA cables, but Schiit sells those too (though you could probably make some for lots cheaper if you know how to use a soldering iron). From what I hear it's excellent.
That or the O2+ODAC from JDSLabs. More expensive, but very highly recommended.
That said, I'm using the DT770s (80 Ohm, not the LE's) with a Xonar DG and I don't feel that I'm missing out on anything. That will change when I go to an external system I'm sure, but for now I'm very happy. I use my system for 100% music.