If variable voltage is your thing, you won't find too many "petite" devices that will also have long lasting battery power.
You can certainly use high voltage mods that are classy, but they won't VV, or they won't be small, or they won't have battery stamina. Size does matter in the world of batteries, especially if you want to draw a lot of power from them and not swap them every couple hours.
The provari or buzz are the common choices for a robust VV device. The darwin looks very wierd to me, and even I'm kind of nerdy, so I don't know that it would suit you, but a lot of people like it. The buzz would be the least expensive, and more in your price range. The provari and darwin, plus batteries and charger, start pushing close to 200+, brand new.
You could also opt for a high voltage mod, that isn't vv, and spend a lot less, and have something far more compact, but you'll sacrifice battery life, in the sense that you'll need to swap them out a lot.
Check the other sections of the forums for lots of video reviews of PV's, before you make your decision. You may find something that isn't as mainstream, fits your budget, fits your style, and you'll be happier with, than purchasing a lightsaber handle to vape from. Or go all out and get a well known one like the provari, and don't worry what people think of it.
Happy B-day anyways
EDIT: And just to reiterate what MickeyRat said, 7volts would be brutal. Everyone is different, but 7volt vaping is just absurd, in my opinion. A big battery, that doesn't voltage sag under load, would destroy almost any juice at that power, regardless of the atty resistance. It would be painful. Almost nobody vapes that high of a voltage, or they use extremely high resistance attys to tone it back down to a usable level, thus defeating the purpose.