When you increase the BCLK to increase the speed of the CPU, the memory also is increased. That's why we have a BCLK to memory ratio. Say the BCLK is set to 100 and your ratio is set to 1:1, this means the memory will also run at 100 in terms of speed (mhz) now let's run a 1:2 ratio. This means whatever the BCLK is, the memory will be double the speed and so on. By defualt, the memory runs at 1600mhz only if the CPU is at stock multiplyer and stock BCLK. You want to find a ratio that will allow a high overclock on the CPU but not overboard on your memory! I would try not to go about 1700mhz with your memory. The bios will tell you what the RAM is running at once you set the BCLK, Ratio and CPU multi speed to.
P.S. i would imagine your RAM is already overclocked as your CPU is overclocked, unless you are running a low ratio!
Go and download CPU-Z and find the memory tab. it will tell you the speed of the RAM. Whatever number is displays, double it for the normal amount. If your over 1700mhz, download memtestzx86, burn to CD and boot from it and let it run tests on the memory automatically for several hours. if you get no issues, your RAM is overclocked and stable
If your RAM is too low in terms of speed, change the BCLK to Memory Ratio. Play around with it and get a balanced setting.
I hope you find this useful
Edit: Maybe your RAM could handle higher than 1700mhz, i really don't know. Test it with memtestx86..