it was explained in the first post.

with the dual 2OHM you can get a final impedance from the pair of subs to be 2OHM. when the amp sees 2OHM, it gives off the 600watts. meaning 300 watts each sub.

there is no better way of using the amp.

with a dual 4OHM you can get a final impedance of 1OHM from the pair, which the amp will also give off 600watts.

but since the amp will see a lower impedance @1OHM than @2OHM, it will run hotter. but im not saying the amp cant handle 1OHM, because i ran my JBL amp @1OHM for a good while.