bang for the buck i chose:
MVP V2 I run a nautilus mini on it
Eleaf 20w I run Vivi Nova tanks on this one
Not saying that the mvp v2 is a bad device but I would definitely not call it a good "bang for the buck" choice at all. A maximum of 11 watts is incredibly low for the new devices these days. Back in its time, it was a good device and 11 watts was not too bad, but it was definitely always a weak mod in terms of power and a good mod in terms of build quality. It's fine for the nautilus.. But it's too pricey for a device that caps out at 11 watts. Even with a built in battery the mod is too expensive considering the minimal power it provides. The iStick 20w is not too bad as far as a good value purchase, but once again it falls short of being useful for someone who wants to use devices that require decent wattage.
The IPV 2S is a good device but if you are dying for more power go for the sigelei 100w+ or 150w (I know the 150w is +50 watts but in my experience the build quality was better on the 100w+ and there isn't much of a need for more than 100 watts). If you want something a little more practical for taking out, I would suggest any of the eLeaf iStick products. Lastly if you just want something new for fun that is slightly more practical, look into the Kanger KBox which is likely the best bang for your buck product on the market typically costing around $25 with a solid enough build quality and 40 watts.
Either way, good luck on your next purchase! Let us know what you decide on!