Well dividers/multipliers tomato/tomato lol. You can use the htt/fsb to fine tune since your obviously more comfortable overclocking that way. But a combination of the 2 is always better.
If you want to make sure the ram is causing the instability (which it usually is with lock up like your experiencing) then run small fft's which is pretty much cpu dependent, so you can rule that out. then nb at stock and blend test. Pretty sure you need more ram vcore and or NB voltage( which also helps ram stability) not cpu/nb tho.