Which port, on average, is after for spl?

What is the major goods and bads of each?

I will be using 1 maybe 2 dc xl 12s and then later 3 level 2 8s or sa-8s.

Um, they can be one in the same. Differentiator is in the size that is required and not related to goals...unless one is keeping the box size down or cosmetic. Obviously moving from 1/2 12's to 2 8's is a big step down for output as well though.