Best headset for FPS gaming?

I play counter strike source and I would like to know the best headset for hearing where enemies are and one that also provides good sound quality. I was thinking of getting the creative x-fi sound card and a roccat kave 5.1 headset. I don't know much about sound so could anyone tell me how effective this sound setup would be and could someone recommend a better one for around the same price (�100-�200). But seeing as this is fairly cheap I think it is rather good. Should I stick with the x-fi and kave?