The recommended third-party anti-Virus software to be added is...
...none.
Your premium-quality Macintosh computer is already well protected, and if something more could make a difference, Apple would have already included it in the box as they do with Backup software, for free.
The malware pinch-point in Apple systems is in making things Executable. Your Mac could be loaded up with malware files everywhere, but as long as they cannot become executable, that stuff is not a threat. System directories are locked and checksummed, so there is nowhere for malware to hide. Applications are sandboxed.
This does not absolve you from the responsibility of being skeptical and diligent when installing things, which:
• provides you with the source site of the item to be installed -- check it for reasonableness -- Flash Player update does not come from HackersRus.com
• asks you to provide your Admin Password to say that you have checked that over and agree to the Installation