How does the Stormcaster's Storm Spell Power ability work?

Question

I am currently in a campaign as a wizard who specializes in lightning descriptor spells. I dipped into Stormcaster for flavor and its Storm Spell Power extraordinary ability. I stumbled across Born of the Three Thunders and may have found some cool (possibly broken) synergy.

Storm Spell Power reads: You are truly skilled in the use of spells that wield the power of the stormy seas. Any spell you cast that has the air, electricity, sonic, or water descriptor is cast at +2 caster level.

Born of the Three Thunders applies the sonic descriptor to any electricity descriptor spell among other things.

Would a Born of the Three Thunders spell be cast at +2 or +4 caster level?

Answer 1

A spell with the listed descriptors would be cast at +2 Caster level.

Storm Spell Power reads: You are truly skilled in the use of spells that wield the power of the stormy seas. Any spell you cast that has the air, electricity, sonic, or water descriptor is cast at +2 caster level.

The text of the ability doesn't state that there is a cumulative bonus if a spell has more than one of the listed descriptors, so the Caster level would remain at a flat +2. However, there's a possibility that that +2 may stack with other increases you may have to caster level, Such as a Ring of Arcane Might, an Orange Prism Ioun stone, or Bands of Spell Enhancement.

A comprehensive list of effects that increase caster level can be found here.

Answer 2

'or'

As long as it has any of those keywords, it gains +2 caster level. It does not gain it more than once, due to how the sentence is constructed, and how sentences work in english, and the ubiquity of that phrasing and it's meaning in the rest of the ruleset.

Also, the strength of that feat is that it forces two saves, one against stun, and one against being knocked prone, making it a magical flashbang, which is amazing in addition to whatever other effects the spell has.