Sigelie 100 watt plus. I absolutely love mine, and it can be had for under $100 on ebay. Just be sure to get some good 18650 batteries with at least a 30amp draw if youre going to be sub-ohming. I use the purple efests with mine and run a .5ohm single coil at 40 watts.
I don't know much about batteries and stuff lol I am trying to learn though lol