Afaik

the X86Config file is for the 3.x.x Xfree86 server
the X86Config-4 file is for the 4.3.x Xfree86 server

so If you have a recent copy of Knoopix (or any other distro)
X86Config-4 is the file you want to edit

But beware, If you change something that you should, this means your with your command prompt and NO GUI to rechange your X86Config-4 file!

Good Luck!