Your NB, is not necessary to adjust for your CPU overclock. It's fine at stock with 1600MHz DDR3 RAM.
My advice for overclocking would be to inch your way up bumping the clock multiplier until it's unstable, then bump your vcore up in increments until it steadies out again (test this with prime95 or IBT). Do that until you get to where you want to be, then run prime95 and IBT and benchmarks that really stress your CPU to make sure your OC is stable.
There are some good guides at overclock.net as well.
Everything I've read states that your NB frequency should be 3 times your base RAM frequency. For example: if your RAM is set to 1600Mhz, the base is 800Mhz so your NB should be 2400MHz. Anything slower than 3 times the base will bottle neck the ram.
That being said, you don't HAVE to do it. Just know that you get the max out of your ram at 3 times the base and any faster on the NB is wasteful.
Currently I have 2133Mhz ram but my system refuses to be stable with a NB higher than 2800Mhz, so while it would be ideal for me to be at 3200MHz on the NB it won't happen and thats okay.