i7-4790K vs i5-7600K

Hello!

Should I buy a used i7-4790K, used Asus Maximus VII Ranger for 400 euros or a new i5-7600K, new motherboard and new RAM for 500 euros?

Thanks in advance!

depends on the intended use, you can check benchmarks for whatever use you need it for.

well it's mostly split, some games run better on the i7, some on the i5, but the i5 has a newer structure, but it's 100 euros more expensive

I'd generally buy new for the warranty.

You can always wait and see how the quad and hexa-core Ryzen CPUs stack up against i5s.