virtualbox.org

I have never downloaded virtualbox before, so I wonderd if I can acctually download the newest version. This since it seems to be a 64-bit version (X86/amd64). And if not, what older version of virtualbox do I use?

Yes it does. It is either 32bit or 64bit.

The "x86/amd64" designation means the package supports both 32-bit and 64-bit hosts. Unfortunately no one seems to have come up with really unambiguous names; there's at least x64, x86-64, and amd64 for the 64-bit architecture and at least x86 and IA-32 for 32-bit.