Yes, DRAM frequencies are safe :)
I have 4400+ Brisbane too, but mine is BH-G2 stepping.
It's running fully stable 24/7 @ 2909MHz with 1,296V. HT multipliers are 5, what gives me 1265MHz HT link speed. Highest freq i'm ever reached is 3392MHz with HT link @ 1475MHz.
So i think you can get...