Just for a bit more insight ...
Go in single steps...start with the very next step up from 600. And try apps like "YouTube", then use your camera, Ect. If your phone does fine (no kernel-panic*) *that's what its called when you "overclock" too high and rebooted your phone.
Also, for this time of testing ...leave "frequency at boot" (or similar) UN-checked. That way, IF u do get "kernel panic" you wont be stuck trying to hurry and turn down the overclock frequency before the phone shuts down. Lol I've been there.
...and just for reference ...I can only overclock to 749....768 when I don't have too many apps.
Lastly, look into purchasing a better SD card. Look at the "class" a "class 8" is good. Then for size....8GB is ok....16GB is better...Ext.
Hope this helps...good luck and enjoy your phone!