You are getting things mixed up. The gpu has exactly nothing to do with your system ram. Nothing. Your motherboard only supports 240pin DDR3. DDR4 is 288pin, it physically will not fit in your motherboard. Your motherboard is Am3+, as in ddr3, you would need an Am4 motherboard to use ddr4. The FX8320 is an Am3+ cpu. It does not physically fit on an Am4 motherboard, and Am4 motherboards are for the new Ryzen cpus.
So the answer is No, you will not get any better performance using ddr4 with an 8320 because they do not work together.
You want better, either buy a New pc, such as a Ryzen or kaby-lake Intel, or learn what your pc really can do, and do it. That means using the fastest ddr3 ram your motherboard will support, buying the...