What is your system and the mode of producing it? Have you got an emulsion, a suspension, or something else?
By definition sonication will only disturb/disperse agglomerates and not aggregates. Agglomerates are typically > 1 micron or so and thus I suspect laser diffraction will be your preferred light scattering technique rather than DLS, but we need more specific details as to what you're doing and the end application.