As I understand it, internal sound cards and what people commonly refer to as DACs are the same thing -- they produce an analog sound signal to pass along to headphones or speakers.
In my case, therefore, since I have a sound card, I don't see the point of having a DAC as I would have to pick between one or the other whenever I wanted to get sound.
As a gamer, I value my positional cues in shooters, but as I understand it, USB DACs don't provide that, so I'm forced to use my Sound Blaster X-Fi sound card if I want the positional cues.
I've been wondering: is it possible to connect a sound card to an external DAC? The idea would be to have the sound card produce a digital signal including the positional cues I want, pass that along to the external DAC using an optical cable, thereby getting higher quality analog sound than from the sound card, and then pass that along to my headphone amp? "Best of both worlds" type thing?