I have a i3 6100 (it's basically like a wired potato) the cooler is a tower cooler. Switching things is not a problem the thing is that apparently dropping 40-60 more € gives me a mobo+cpu that even beats my main computer
Are you able to keep all 4 of your processing threads fully loaded?
Your I3-6100 with 4 threads has a passmark rating of 4169. That is when all 4 threads are fully loaded. I might imagine that would be the case with several VM's.
The single thread rating is 2235.
The i7-7700K has 8 threads and a rating of 9689/2745.
I3-12100 (8) 14540/3550 would be better.
The 5600G (12) 19825/3188 would, indeed be a big jump.
If budget permits, look at the I5-13400 (16) 26206/3836.
How good do you really need to be?