This mod.
Runs to ~$180-ish the way the exchange rates are at the mo'.
5A limit, 3-5.8v, 2xAW IMRs (1600mAh each - 2-3 days of fairly consistent vaping from it).
Can happily reach 25w but you have to be aware of your resistance to get the best of the amp limit - a 0.8ohm coil can be pushed with 3.9v whereas a 1.3ohm coil can have 5.6-5.7v through it before the limit kicks in on mine.
Incredibly tough mod as well, doubt you'd do much if any damage to it unless you rolled a tank over it. Pain in the hole to get serviced from America, but that's how the rest of the world feels about the ProVari, so...