You get Studio One Artist for free, when you buy a PreSonus hardware product. Updates are also free (within one version), but 4.6 has indeed seen a major change. The completely new developed Ampire has become a "state space" plug-in, which can be used in any DAW, not only in Studio One. The Fat Channel plug-ins are also available in VST3/AU/AAX formats now. We might not really like the decisions of PreSonus, but who are we to critize them? Artist has the Ampire plug-in with one amplifier model, so if you want all the "rest", why not buy the set? Here is some additional information:
"Ampire is available in VST3, AU, and AAX formats for a U.S. price of $59.95 from the PreSonus Shop. Studio One Prime and Artist users can upgrade their Ampire experience with this Add-on. Studio One 4 Professional users will receive a complimentary license for Ampire in VST3/AU/AAX formats."
This is the link to the Ampire add-on for Studio One Artist: