The price difference between x30 624mhz and 312mhz is $100. I guess 520Mhz should about $30 cheaper than 624mhz, which is a pretty big material cost saving. So don't expect 520Mhz can be overclocked to be about the same capabilty as 624Mhz.
ASUS should think about the wifi-bt combo model using 624Mhz.
