I'm never that keen on putting volume knobs up to the max on most keyboards. For starters, if you have a quiet user style or something not balanced right, you've left yourself nowhere to go. But the main thing is, crank up your home monitors (or do it on the PA at a setup) then crank up the arranger to the max (but don't play), and you tend to hear an increase in low level white noise from the op-amps being pushed to the max. Dropping the main volume tends to make that go away almost completely.
Personally, I tend to use my gear at around 75%. That way, I'm in the decent area for s/n, but still have a bit of headroom to account for the odd quiet style or SMF. And in your case, Donny, the odd mp3 or .wav.
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An arranger is just a tool. What matters is what you build with it..!