In order to find out which version of AMD Crimson you need to download, we suggest to run the AMD Autodetect Tool.
From developer's page:
Whether you are a videophile, gamer, professional developer, or simply want a better experience from your AMD-based PC, there is something here for everyone to love.
AMD Catalyst updates are focused on improving graphics performance, including enhancements for popular DirectX, Mantle and OpenGL game titles.
Every AMD Catalyst driver release undergoes exhaustive testing but we set the bar even higher with this latest driver release. In addition to increasing our automated testing by ~65% with this release, we also welcomed direct feedback from our most critical users on six of the largest PC communities -- all to ensure a user experience as intuitive, reliable, and enjoyable as possible.
For details about driver and Operating Systems compatibility, highlights of AMD Catalyst 15.7 Driver for Windows
and other info, see these Release Notes