I picked up an IPV v3 (150w, dual 18650, subΩ down to .1) a couple weeks ago and absolutely love it. May want to check it out. For $125 shipped, including a charger, kinda hard to go wrong.
With dual coils the resistance will be half of the single coil assuming both coils are the same. For example, if you build two identical 1 ohm coils the resistance will be .5 ohms.
You should look for the real wattage that have been tested, lots of high watt boxes don't come close to what they say...just sayin'. Good luck.
it seems that there'll be a future upgrade of software for higher wattage?