It's not required but it's convenient.
Anyway, here you have the complete list of Corsair memory which is compatible with your mobo:http://www.corsair.com/configurator/product_results.aspx?id=1048887#other_modules
The lower latencies and the higher frequency, the faster memory.
I would recommend to you this one: CORSAIR DOMINATOR TR3X6G1600C8D 3x2Gb DDR3-1600Mhz CL8.
From Gskill you have available the following ones:http://www.gskill.com/configurator2.php?pid=2&search2=UDZUIFNF&model=970
This one has the same features as the Corsair one:
GSKILL [ Ripjaws ] F3-12800CL8T-6GBRM http://www.gskill.com/products.php?index=235&c1=&c2=
3x2Gb DDR3-1600 CL8