well if you want to try a 5v mod, take a look at the GLV. I have one, and just love it. I got it with the 510, then bought an adapter to go to a 901, and have found my new favorite atty. This (to me) is the perfect set-up, the flavors have come to life, for instance DIY Flavorshacks mallomars, which was good at 3.7, just rock at 5v. I can really taste the marshmallow now that I couldn't distinguish before. There are so many and this probably isn't going to be a very easy decision for you, but be patient and you won't go wrong.