I personally used to use cartos and found them very lacking, as they don't hold their juice for a very long time and the clearos, like your CE4, seem to hold the liquid much better, IMO. If you like the tank that came with it you could try an upgrade to the Vision Novas. They are great and can hold 2+ ml of juice. I would personally recomend this vs any carto. Also they are cheaper to replace. You simply replace the coil for around 3USD. And those coils last a very long time if you treat them well and clean them. I am still on the same one for the last 3weeks.