After about 3 days of digging as to why I can't connect my Samsung Galaxy S3 via USB to my 300, I found a root cause for my issue. Samsung (and other manufacturers) changed their USB protocols from "Mass Media Storage" to "MTP/PTP" (Media Transfer Protocol), which, of course, is not compatible with the 2012 8.4N or many other devices, including PC's.
However, I couldn't find a fix for my 300. It would probably require loading the drivers manually on to the head unit which, if even possible, probably wouldn't even accept them.
Yet another example of Big Businesses screwing their customers for the sake of exclusivity and monopolizing their corner of the market. So screw you, Samsung!
I returned my Galaxy S3 and am sticking with my HTC. I don't care if it's last year's model. At least it works!!!