I've read here that you should contact Magix via your acct or by calling them if you don't already have an email offer for upgrade that they send out apparently from time to time...... Should be an option within acct far as I'm concerned.
Further to what Greg said, I suggest that you login to Support and raise a request for an upgrade price from 2015 Basic to 2016 Premium. Remember, 2016 is now out.
Good addition John, I'm new and forgot about the Support login page to create a Support ticket :)
Need to do a few of those myself I think....... I just got the 2016 Live (is that considered premium this year?) and have a few questions issues with it and the Music Studio 2016 mine came bundled with..... So far pretty good with a few short looks on my older Win 10 running laptop......... but I don't see dual core support options... maybe that is in Samplitude version of Music Studio only?.......... I have the Samplitude 2015 trial loaded also and did see it there, works great far as I can tell too! Tmi for this post, but thought I'd throw all that out there for OP to consider, may help....
Good News! It looks like upgrades from within program are coming! I just noticed that my version of Music Studio 2016 has option in help menu to upgrade to Samplitude version! I clicked it and it gives info screen and then links to a special upgrade page I've not come across before on site! It listed a special discounted price! So soon the email for upgrade offers will not be nessesary possibly! :)