Which of these size enlarging options for a barbarian stack?

Question

I'm just interested in theorycrafting. The barbarian class provides two mechanisms of growing a character's size one step:

• Titan Mauler's Titanic Rage
• the bloodrage power: Abyssal Rage

There are also additional sources of increasing one's size. Using the eldritch heritage feat line, one can pick the sorcerer bloodline ORC and thus gain Power of Giants.

Of course, the friendly mage cast or one, via items, can employ Enlarge Person to help a bit.

Which of these options stack and what size category will be gained?

Answer 1

So, of course, the principle obstacle to stacking size alteration is:

Multiple magical effects that increase size don't stack.

(from the CRB in the Enlarge person description)

So, only one of the magical effects will increase the character's size. All of the effects you have listed are magical in nature, either because they are a supernatural ability, a spell-like ability, or a spell. The final size of the character in question is one larger than whatever their base size was.

Lastly, if you are playing with the Dreamscarred Press psionic rules, the Expansion power was ported over verbatim from 3.5, and provides the even harsher rule:

Multiple effects that increase size do not stack

rendering whether or not the effects are magical moot.