I have done a quick comparison of the features of both 19 and 20, what I mean by that is what one offers versus the other on JRiver own Site, and from what I can tell,nothing seems is there to prompt me to upgrade to 20.
Yes 19 offers memory play too,in response to Jarcher,s post above.
In response to Daedalus, first sorry to hear of your troubles, my set up is 2011 macmini running Yosemite, MC19,USB out to Emotiva Stealth DC-1. Before Yosemite, I was on Snow Leopard,too with no trouble, the occasional crush yes,like I said,it only happens when I play around with JRIVER settings,while on play mode.
What macmini you have?.
George