mind that I give u a advise don go for the extreme gamer sound card better go for this 1 cause will be more functional compare that u are using for gaming so pls have a look http://creative.com/products/product.asp?category=1&subcategory=208&product=14000
if u want more simple way to oc was that you getting a HIS X1650XT I-turbo will come with a build in software to control it .. then the clock speed was 630 core and memory 1460 maybe u can tune more around in 4% extra margin as I try with no problem ..
this was the link for it...