Are the siberia v2 7.1 surround? As I would only get them for my csgo compet matches otherwise I'd just use my hd600. Also would plugging them directly into my motherboard be better? My motherboard is the Gigabyte b85m-d3h which has 7.1 audio.
Well yea, plug them directly into your motherboards headers..
But what I would suggest is, try both.
It might be that your onboard audio is not as good as the external card.
But to my guess, it should be better.