another mod which you haven't thought of is a sx350 chip. You can put it in a box like the 1590A with a 510 connector from fatdaddyvapes and get it for about $100 or less if you build it yourself. Then you could buy a kayfun lite + v2 from where ever you like and a bat (vtc5). Your mod would also tell you everything you need about vaping, watts and voltage that's going to be firing at. Just my .02 worth.