Upgrade recommendations

Hey everyone. I want to upgrade my current build because I have the feeling that my CPU is holding back too much performance. And I think I have some micro stuttering because of the 1% lows.

Current build:

CPU - Intel I5-10400f GPU - AMD Radeon RX 7800 XT RAM - Corsair vengeance RGB Pro DDR4 3600 mhz 32GB Mobo - Asrock b560m steel legend PSU - Thermaltake GF3 850W 80-Plus-Gold

I have a small case so mATX is preferred but I could buy another case if that’s better. I live in Germany my budget is around 300-400€ I don’t know what makes more sense. Just an CPU upgrade or CPU+Mobo. I want to stay with DDR4 ram because of the prices.

ChatGPT recommended an Intel I5-14600k + MSI MAG Z790 Tomahawk WIFI

Thank you for your help