Unless you're going to be doing heavy overclocking, the stock cooler (Wraith Prism) that comes with the 2700x is actually really good, dare I say fantastic if you don't OC. If you do intend to overclock, the best of the best air coolers would fit into your budget - Noctua NH-D15 is renowned for its superb cooling efficiency and silent operation, only downside is that it looks horrendous imo. The be quiet! Dark Rock Pro 4 is basically the same, only it looks way better. At about half the price I've heard really good things about the Thermalright Macho (Rev. B) and the Scythe Mugen 5 (Rev. B).