I beg to differ, you can get 3.2 Ohm heads for the VIVI Nova, and set your voltage higher.
OP I don't have a Provari, but my gripper hits like a mule, and I prefer the clearomizer systems. VIVI, Vision 2.0 (adapter needed), and the like work great for me. And with the vision tank you can get a 4.0 ohms head for it, and go very high with the voltage.