where to find most recent version downloads?

So ive discovered that a lot of my issue appears to be that im out of date, my version is only 4.6 and I understand there were some php updates in later releases that might explain why im having problems trying to do a new install on up to date os/apps.
So my issues is simple, what is the most recent version of fusion/classis, and where do I get the appropriate files under my perpetual license?