The Roland PM-3
sounds like an interesting option Clif. Are you actually using this setup on your arranger rig?

My concern is whether this system has been "optimized" specifically for drums & percussion and not for vocals (even though it says you can use it for keyboards).

Do you happen to know the weight and dimensions of the sub-woofer? The subwoofer looks heavier than my KC300 (38 lbs).I couldn't find any PM-3 specs on Roland's US web site.