Fx Cpus are @50% slower IPC than new Ryzen, or @upto 60% slower than new Intel. Per clock. If you figure an i5-8400 at 4.0GHz, to get similar IPC the FX would need to be closer to @6.4GHz just to keep up, and thats not including any instruction sets, Lcache improvements, motherboard improvements, storage improvements etc that'll facilitate added ability. An 8400/1070 is a pretty well balanced setup, capable of maximizing ability at 144Hz. The FX cpus will be considerably higher cpu usage as core bandwidth is swamped and fps will be in the toilet.