This
http://www.zalman.co.kr/usa/product/view.asp?idx=113 will turn any headphone into a headset.
I'm quite partial to the Medusa purely for gaming. They're heavy but comfy and they do actually work for me (the 5.1 bit that is). The problems range from an interference-prone dedicated amp (a buzzing noise is present unless you make a real effort to site the amp away from sources of interference) and also it requires quite a bit of setting up time to get the channel volumes working for you. If gaming is all you do with a headphone, the Medusa is a decent choice at UK prices of around £45.
The recommendation will depend on what else you're planning to do with the phones.