Errr...after I wrote this I realized I hadnt read the second page in which you already purchased one...

h idiot me:
I don't think you can go wrong with a Provari. Even users who originally say they dont need a variable voltage unit often wind up using it and liking it...I personally fall into that category. Also, you will get an incredible series of safety systems built into the Provari, and won't have to worry about the exploding eGos anymore.
The current model is called the V2. The older model was the V1. The current offerings come in 2 sizes (mini and regular), and three LED colors (red, blue, green). As far as buying, you buy directly from Provape, the maker, if you are in the US...
So do you want a mini or a full size?...what color LEDs?
ProVari Variable Voltage Ecig: Best Variable Voltage E Cig Available!
ProVari Variable Voltage Ecig: Best Variable Voltage E Cig Available!
With the mini you can use the 18350 battery and with the extension the 18490
With the regular size you can use the 18490 and with the extension the 18650
From my usage, I would say that the 18490 will give roughly twice the run time of the 18350 and the 18650 will give roughly twice the run time of the 18490. Each extends the unit by about 3/4 of an inch. I personally use 18490s the most as I have around 10 of them. They give the best tradeoff of size and run time duration. The regular size with the extension is too long/heavy for me and the mini without the extension doesn't last long enough. But all of that is my opinion, and you will find the 'ideal size' depends on your own needs and preferences.
Also, consider buying the Pila battery charger (if not, an XTAR)...the Pila is one of the, and possibly the, finest charger ever made, and it makes recharging not only faster, but safer. People often cheap out on chargers and this is a bad idea. Remember that if a charger does not correctly terminate the charging of a lithium ion battery upon the battery reaching its full capacity, the battery will eventually be overcharged so high that it explodes (this is an issue that the eGos/eGo clones seem to have that happens quite frequently relative to other model PVs). Lithium battery explosions are violent and usually set whatever is in their immediate presence on fire. This is not a good place to save money. If you use a Provari with AW or Panasonic batteries and a Pila or XTARii charger, you have the safest and best performing combo that the industry currently has to offer.
Best Rechargeable Battery Chargers: Pila Battery Charger & Pila Charger
Battery wise, only use IMRs, which have the amperage needed to run this unit correctly. Provape sells AWs which are great. Panasonic makes some IMRs which also function the unit without issue, but they are only available currently in 18650 sizes.
You can use eGo components but you need to buy an adapter...
Ego-T Adapter
As far as tanks go, many tanks fit the Provari and there are a lot of tank makers. I have become a firm believer in the pyrex Phiniac tank, which not only looks awesome but performs flawlessly. I'm sure others here have their preferences as well, so that is kind of a personal preference thing.
The Provari will wash your dog and cook your breakfast. It will fill it's own cartomizer and make cheap juice taste like your favorite cigarette. If you buy anything else, you are throwing your money down the toilet. Everything else is garbage and snake-oil. The Provari will cure your asthma and prostate cancer. It will withstand a 20 ton hydraulic press and work in 800 feet of water. The first man on the moon brought a Provari with him.
O.K. That about covers it.
Provape.com
This is the best post I've ever read in my life..