Well, Not sure but I've heard that the M5A88-M overclocks well.
You can OC your mobo to run 1600Mhz memory, or else the mobo will automatically downclock it to 1333Mhz.
You can get the 1600Mhz memory, run it @1333Mhz & maybe in the future OC it to 1600Mhz. Or you can save some bucks and buy 1333Mhz ram.
FYI, There isn't much difference between 1333Mhz & 1600Mhz. So, its really your choice.