Have you tried the gpu in a different slot? that board has two PCI-E 16x slots, the slot second from the bottom (third if you count the PCI not so E slot) and the top full sized PCI-E slot
The zalman mic imo isnt good enough. It is worth the price it costs(10$). I had one and people were complaining about background noise being very bad. I was using it on a Asus Essence STX.
I can say the Siberia V2 is extremely comfortable. I havent had one headphone that feels light and in place like it. As an exemple my ATH-AD700 is light but not "secure", it moves easily on my head.
The cushions on the V2 are pleather so if you sweat a lot, it might not help it. Imo pleather makes it hotter than open headphones with mesh and the likes.
The Mic on the V2 is pretty awesome. You don't have to pull it out and people will hear you clearly.
Important note : ATH-AD700 isnt in the same league audiowise. (its a lot better, less bassy, more accurate imo) I was just mentionning the feel when wearing it.
Another note : I now use a ModMic as a microphone because I wanted the better sound quality vs a Siberia V2. ModMic is about 30$ and can only be purchased from their website AFAIK.
More note : If you already have a webcam, maybe the mic on that would be enough and you wouldnt have a cable laying around on the desk if you get a zalman/modmic or any standalone mic.