i started with a ce4 but that was it
i heard a lot of good stuff about pro tanks also but i dont know if i want to spend the money for one of them
ProTank can be very good, but they also can be somewhat finicky. Not sure what it is about the iclear30 you don't like, but it is a Top Coil device as is the Viva Nova, they require you to tilt and swirl to keep the wicks wet and avoid dry hits. Not a problem for me, but I lay my stuff on its side between vapes.
Things like the ProTank and Evods are bottom coil devices, they don't require the tilt and swirl action, the wick is at the bottom and tends to stay wet.
Top Coil(iclear 30,ce4,viva nova,ect) normally have a warmer vape.
Bottom Coil (protank, evod, t3, ect) normally have cooler vape.
I actually use both, however a lot of people seem to prefer the bottom coil, like stated before, it is all subjective. What works for one may not work for another.