Sound question

[Zafira.7560]

I'm playing my computer sound through an optical connection to an AV receiver with a 5.1 speaker setup. The receiver has the option to decode the sound in many formats. Rather than just picking one that sounds the best to my ears, I'm wondering how I should process the sound to get the sound the developers intended. Another way to phrase the question, is what sound coding, if any, is used in the GW2 sound feed?

Choices on my AV receiver are Stereo / Dolby Surround / DTS Neural X / DTS Virtual X / Multi-Channel Stereo / Video Game / Virtual