Looking at getting a new stem but don't really know what to get.

I want something that's stiff and lightweight. Something awesome?
I need 120mm, 6deg, 31.8

EC90 SL?
EA90 ?
3T ARX?
Zipp Speed(this one is kinda pricey, worth it?)
FSA SL-K?

WTH is the difference...Should I go carbon?