My X4 has a much hotter signal than the Millenium sound module. I expect the XD3 does also. In a larger venue, in order to get the volume you want out of the Millenium you may need to turn the KP-200S master volume up so that you have a pronounced "pre-amp hiss" (see manual page 3). This may or may not be objectionable.

A mixer means another piece of equipment to set up - which may not matter to you.

You may find that passing the Millenium signal through a mixer "darkens" or "deadens" the sound a bit (higher overtones less pronounced). At least it seemed so to my ears when passed through a Fostex mixer or a Behringer UltraLink Pro. That may be OK to your ears.

Good Luck

RJM
Good Luck