Sennheiser G4ME ZERO sounds horrible.

[mamalrlr]

Hello,
Today i've just received my Sennheiser G4ME ZERO. I've heard a lot of good things about it, and struggled a lot to choose between this one and the Hyper X Cloud Revolver S, but I chose this one.
So, I connect it to my pc, and i'm like : What the hell is this ****??
Now, i'm looking to buy a new sound card, or a motherboard, because I think the problem comes from this. So my first question is, should I change the motherboard or get a new soundcard ? My motherboard is a Gigabyte Technology Co. Ltd. B75M-D3H, and I've never bought any soundcard.
My second question is : If you tell me that changing my mobo is better, will it affect something about the CPU or anything ?
And my last question is : If you think that taking a soundcard is better, can you give me a good model of soundcard for playing and listening music ( because the bass on the game zero is pretty low, I would like a bit more ) ?
Thanks,
iNoxiS
PS : Sorry if my english sucks, i'm not english.

 

[mamalrlr]

Oh, and, forgot to say : people can hear the audio from my pc, even if I mute the microphone ( directly on the headset ), and this happens with both my old Logitech G230 and my new Sennheiser.. I don't know what's the problem but I was thinking about the sound card / mobo again ^^
By the way, I would need a pretty fast answer if possible, so if someone have the time to answer me it would be kind.
Thanks,
iNoxiS