[Peculier]

Firstly, I am new to desktop audio.
 
I have always been running my music out of a MacBook Pro via USB to a Yulong D100 Mk2 DAC/Amp. However I play games on my PC, which I built for gaming, and it has an Auzentech X-Fi Prelude sound card. I am considering playing my music on my desktop, because I have much more hard drive space on my desktop (3TB, to be exact). But I was wondering if using the Prelude sound card out to an external headphone amp like the Schiit Asgard or Lyr, is better than bypassing (if its possible, or better to do so) the Prelude sound card, and using the Yulong D100 DAC/Amp?
 
So my 2 choices of audio chain would look like this: Desktop > Prelude Sound Card > Schiit Asgard/Lyr > HE-500
 
OR
 
Desktop > Yulong D100 DAC > Yulong D100 Amplifier > HE-500

 
Also, in general, do external DACs sound better than PC sound cards? I don't really want to get a new sound card, but if sound cards are generally the go-to for great sound on Desktops, I may be willing to get a better one (suggestions required). In the event that using an external DAC is generally better than using a soundcard, I WILL upgrade my DAC and Amp in time.
 
All of this is done with Hifiman HE-500s, which I adore.

 

[NA Blur]

In almost every case external DAC units even fed via USB will sound much better than internal soundcards.  This is because the USB is much more isolated from the noise of the motherboard, mouse, various clocks, and other power components within the PC.  I went from a soundcard to a Bithead years ago and have not looked back.  I originally could hear the "bleep bloops" of my PC's inner workings as well as a high pitched squeal when I moved my mouse.  Once I allowed the Bithead to bypass the soundcard's DAC all of the noise went away.
 
I have heard the optical is even cleaning than USB, but I could never get mine working.
 
I am borrowing a pair of HE-500 and through an m903 I can say they are quite possibly my favorite headphone.  I need to listen to some LCD-2 Bamboo to be totally sure they might not be even better, but good choice on the HE-500.

 

[NamelessPFG]

External USB DACs mean you lose the X-Fi Prelude's gaming features. (There is a little trick in Windows 7 that may work around this, but I can't vouch for the sound quality.)
 
That is obviously not desirable; you'd have to use S/PDIF from the Prelude if you really wanted to use an external DAC.

 

[Peculier]

Ok so if I connect the DAC via USB then I will be bypassing the Prelude card correct? But for all intents and purposes, it shouldn't be any different (SQ-wise) if I just continued to run my music out of my MacBook Pro, so I guess I'll stick with that, and use the PC just for gaming. Thanks!

 

[NamelessPFG]

Pretty much, since any audio device that connects through USB has its own "sound card", so to speak.
 
Dedicating audiophile-grade music playback to one computer and dedicating the gaming computer to the best possible gaming audio is probably the best way to go, if you want to get the most out of both.