You are coming at this the wrong way. €5k is more than you need for a top end setup, you can spend more but generally it’s only asthetics that improves.
What you want to do is say what you want. Do you want top settings at 4K but lower Hz or a lower resolution at higher Hz. Are wanting any accessories like a racing sim setup.
You can build an epic pc for €2.5k but you can tailor it to your needs. Sending €5k most likely won’t give you any material performance gains.