Need Help In GPU And Processor

Hi All! So i am building my first Gaming PC but i am confuse about the GPU.I am thinking about AMD Radeon R7 250 2GB.I have saw several gaming videos on this Graphic card some videos shows great performance some shows very low performance i cant decide.I want to play high end games on this like GTA V,Battlefield 1,Overwatch,Mafia III and many more.so i am asking you all if someone has use this card please let me know the performance of it and if there is any good card in this price of range or little bit more expensive then this please let me know.Also i am confuse about choosing the Processor.There are 2 options in my mind AMD APU A6-5400K with Radeon HD 7540D and AMD APU A4 6300 with Radeon HD 8370D.Which processor is best and will be suitable with 8GB DDR3 Ram?