in this day and age of RAM dividers, you really don't need to stress out your RAM (if you have weak ram). All things being equal, CPU speed rules. 2 PCs at the same CPU speed, the one with higher RAM frequency would probably benchmark better. but would you notice it in day to day use? Most likely not.
Increasing RAM voltages helps to stabilize an overclock.... as does relaxing the timings. AIRFLOW over your ram sticks work better to cool them off than RAM heatsinks (which are nice to look at through a windowed case).