Astro A*Star MixAmp Help?!?

Alright so when Christmas comes im planning on buying some Astro A*Star In-Ear Headphones. i am planning on using these for both my ipod and my xbox. So in order to use them on my xbox i need a Mixamp. I am a new costumer and i NEED to know which Mixamp i have to buy. Do i buy just the regular Mixamp or do i buy the Mixamp 5.8?!? Please Answer!