But as I said, the sound for now is crappy, like, really bad. It can't be this bad for this price..

I just bough a Sennheiser Game Zero and the sound I hear isn't the one that should get out of it, for sure. My Marshall Major II sound so much better, so I suppose that there is a problem.. I tried to plug it on the motherboard at the back and on the front panel but nothing to do, the sound is...