Id second the MVP, they are great mods.
A protank or the new protank 2 on top of that mvp will be amazing.
The only drawback on that is its better to have a good backup, you don't want something to break down and have to resort to something not as good.
If you want to stay with ego sized batteries a kit like this
Kanger Evod Starter Kit
They aren't variable voltage but they run @ 3.7 volts, with a 2 ohm evod they hit fantastic.
That link Uncle Willie posted above me is the best deal you'll find for a ego variable voltage, you can get 2 of those and order a few evods from mbv (which are the cheapest ive seen) and they will be real a kanger product. stay away from fasttech clearos till you have more experience because most likely you could get a chinese knockoff that will be terrible.
It does take orders from fasttech about 2 weeks to ship also.