Your USB headset won't show up in the Realtek HD Audio Manager because it is not managed by the Realtek chip on the motherboard. It's getting raw data.
Did the kraken come with sound panel software that you can install? Otherwise you will have to use either in-game controls or the default Windows mixer.
EDIT: Razer's site says "The full potential of the Razer Kraken 7.1 is unleashed by its advanced 7.1 virtual surround sound engine. Driven by Razer’s powerful Synapse 2.0 unified configuration software, this highly customizable engine modulates sound to simulate a 360⁰ surround sound experience,..." (
http/www.razerzone.com/gaming-audio/razer-kraken-71 ) , so I guess you need to find the disk that came with it or install the Synapse software and try it. Its page is here: http
/www.razerzone.com/synapse2