Worth it to put headers on a 318?

If you went from single exhaust to dual, you've already doubled the capacity of your system. If you went from 1 7/8 to 2, 2 1/4 or 2 1/2 you've made additional improvment.

Factory spec says a 150HP 318 gets to 170HP (20HP gain) with duals.

From that chart, it looks like the factory hipo gives you a 5-7 TQ gain and 5HP over 318 stock, and the headers all were another 5-10 TQ and HP.

So the question is what ammount of price and headache is worth what gain.