Two is an overkill IMO for all but the loudest bands, especially since the sub takes the load off the CSS below 100hz, or higher if you desire. I never have the volume past 12:00, but advance the keyboard and mixer to 1:00. I have plenty of headroom, and it is loud with my pedal at 2/3.
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pa4X 76 ,SX900, Hammond SK1, Ketron SD40,Ketron Event X Centerpoint Space Station, Bose compact