From what I have seen on here, there isn't any M-Powered on the new versions and MYOB definitely won't be upgrading any Classic version for STP. I suggest you read this forum about the new versions as you will find there are still a lot of problems, including being incredibly slow (especially with larger files that cannot be purged), they have a lot of crashes and long standing bugs, and they are costly. I have kept all of my old clients on perpetual licences with v19, which is fast and reliable, without subscriptions and without support without a problem so far - I do advise that they have good backup protocols including the programme installers for this to ensure longevity of the programme.
You don't have to upgrade for STP. The ATO has the below announcement on their website: MYOB is also developing a Low Cost payroll STP solution for Micro-employers so this may apply to you.
"Employers with 19 or less employees
Parliament has passed legislation to extend STP reporting to all employers from 1 July 2019.
Talk to your software provider to find out what you need to do to update your software and start reporting.
Different STP reporting options will be available by 1 July 2019 to help smaller employers. However, we won't force employers with 19 or less employees to purchase payroll software if they don’t currently use it.
We have asked software developers to build low-cost STP solutions at or below $10 per month for micro employers – including simple payroll software, mobile phone apps and portals. A register of providers who intend to build these solutions is available at Low-cost STP solutions.
Micro employers (1–4 employees) will also have a number of alternative options that are not available to employers with 20 or more employees – such as initially allowing your registered tax or BAS agent to report quarterly, rather than each time you run your payroll.
Exemptions to STP reporting will also be available if you have no internet or an unreliable connection."
If you haven't already signed up to the ATO's Small Business Newsroom, then I suggest that you do as this provides a lot of useful information regarding STP and other business information "straight from the horses mouth." Do your own research as it is a big change and could be very costly and frustrating for you to just upgrade when you can without assessing all of your options. If you do go with the upgrades, I seriously suggest you keep running a parallel v19 as you may decide to return to it if the new version doesn't work for you. Others on this Forum have done this and even more have given up and left for a different software provider. Hope this helps and feel free to private message me if you would like more detail.
Cheers
Liz