You can't stream on a 4 core cpu - well, not that you CAN'T but quality drops drastically, because games using any number of cores + background processes + obs = your I5 can't realistically handle all that.
Do you have a set budget? The the best cpu for your motherboard that can also stream is the 7700k, BUT for the price of that cpu, you can get this:
PCPartPicker Part List
CPU: AMD - Ryzen 7 2700 3.2 GHz 8-Core Processor ($209.99 @ Amazon)
Motherboard: MSI - B450-A PRO ATX AM4 Motherboard ($79.89 @ OutletPC)
Memory: G.Skill - Ripjaws V Series 16 GB (2 x 8 GB) DDR4-3200 Memory ($68.99 @ Newegg)
Total: $358.87
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-06-30 19:03 EDT-0400
...and it would perform even better! All for about the same price as a 7700k!