Actually, with the Barbetta Sonas you won't need a mixer, but for a 600 person venue you will need to use two of them and place them on stands. The Sona 32 has a great, built-in mixer and provides all the power you'll need for the type of jobs you described. When I recently switched to a pair of Sona 32s, I eliminated my mixer and lots of other components.

Good Luck,

Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!

K+E=W (Knowledge Plus Experience = Wisdom.)