Question about links

Hello.

(sry for bad english)

What do you think, will be best links for 100% chaos FireStorm totem build. (DPS at bosses)

1) Firestrom (Probably the best for firestorm :D )
2) Spell totem
3) Void Manipulation (double dip initial hit+posion scaling)
4) Conc effect (also double dip? Im not sure)

And right now im not sure. What should I take for 5 and 6 link?
-Inc duration (duble dip, longer posion and fire storm)?
-faster casting (more hits per sec, so also mor poison stacks)
-elemental focus (only initial hit)
-controled destruction (only initial hit?)
-empower (initial hit only?)

Or maybe something else? Im really confused, please for help people. I dont even know, how to calculated it. It is to much fr my small stupid brain. :D

Greetings! :D