idk if my i5 3570k would bottleneck my rx 580 8gb as i guess 3570k is a bit out of date.
so what cpu do u recommend?I wouldn't be too concerned about that. Per-core performance of processors hasn't been advancing that quickly in recent years, and an i5-3570K should still be roughly similar in performance to the current quad-cores from Intel or AMD. Those are now positioned as budget models (i3 or Ryzen 3), with higher-end processors getting more cores and somewhat higher clocks, but even those should be fine enough to run the vast majority of current games quite well. With a more mid-range card like an RX 580, I doubt the CPU would limit your performance much, assuming you're targetting a resolution of 1080p or higher in recent games.