No, that was 1:1 when I had my Crucial Ballistix. That RAM was stable all the way to 300, but the CPU wasn't.
No, that was on my XP90.
There are no guarantees in overclocking. You might not even get another 100MHz out of an FX57 (doubtful, but could happen). Just because my CPU can get there dosen't mean yours will. You could do better or worse, its all down to luck.