It depends on what you need from a Kindle. If you're new to the world of eReaders, spending under $100/£100 is a good starting point to see if you enjoy the experience. Spending slightly more to get the Paperwhite is the sweet spot for most people, with the extra features on the Signature Edition not justifying the extra spend. Unless you really want a different design or large screen, there's no reason for most people to spend over $200/£200 on a Kindle. That's especially true of the Oasis, which is now over three years old.