I'm also using an X4 and find the same as RJM does. The output signal is hot enough to be injected directly in my compact PA. The PA has a gain control to adjust the signal level at the amplifier input to avoid distortion. Ajusting this gain properly, I seem to get the strongest possible signal, so I normally don't use a mixer in my gigs (unless, of course, I need to use more sound sources).

-- José.