Pure broscience? Ephedrine + caffeine has more data than pretty much any weight loss combination...ever.
That said, I would exercise caution and probably advise against combination with an SNRI. One of EC's modalities is as a catecholamine releasing agent. If you're cutting off reuptake of NE, there is now way COMT can compensate, which could create an adrenergic crisis if you take a releasing agent and go exercise.