What I think they'll say to you about the single tweeter verses an array is that if the midwoofers are an array, then a point source tweeter is sort of mismatched. A point source delivers a different coverage pattern than an array, and so if you mix them, you'll have different sound characteristics from the tweeter than from the midwoofers.

Anyway, FredT300B started a thread about array kits a while back that you might be interested in. There were a few mentions of array kits there.

Wayne