If you don't want ACT to do any combat log parsing, just set the Log File Input Language to "(None)". That way it's only taking CPU time to parse your triggers(and time stamps) and no additional memory to store combat data.
PS: My start into log parsing was EQWatcher plugins.
That aside, it is technically possible to make a UI mod to play a sound when a certain maintained spell drops... but you would be restricted to the list of sounds EQ2 exposes to the UI.