You have a 2011 Mixamp Pro. You'll need this cable if it doesn't come with it http://www.amazon.com/StarTech-com-MUYHSMFF-Headset-Splitter-Adapter/dp/B004SP0WAQ/
Also, make sure you have an optical cable too.
And yes, if you don't care to use the chat features, just plug your headphones in directly.
Edited by calpis - 6/15/14 at 9:48pm