Krak - The two are mutually exclusive. Over all flexibility would be hands down installing an EQ. Typically those are more expensive then the built in features of the Tbox or tonal switches built in the XM9's.

The switches on the XM9 effect the horn function. The speaker doesn't have a tweeter as mentioned above.
The throttle box is not a notch filter. It manipulates the phase of the horn from narrow to wide.

Both features are subtle changes at rider distance.
An EQ of any brand, would offer dramatic changes at all distances.

If you'd like more detailed info, shoot me a pm.

-Brian