OK FOLKS, my FOLLOW-UP. I can NOW finally say I am satisfied with my decision (thanks for your assistance Ploki). I finally running EVERYTHING I used to run on my MacPro, and can play back MOST of my songs I tested without any changes to plugins. To get there took about 4 VERY FULL days work (including nightshifts). The DRAWBACK? I had to pay a LOT of extra bucks to update nearly ALL software to the newest versions. The entire investment (Hardware plus software), and 2 new 4k Monitors, came to about the same I would have paid for the BASE MODEL 2019 MAC PRO.
Mac Pro 3,1 (8-Core, 32GB RAM, 4TB, El Capitan), Mac Mini 2018 (6-Core, i7, 32GB RAM, 2 TB, Catalina), RME Fireface 800, Logic Pro X, Native Instruments KOMPLETE 12, Superior Drummer 3, Applied Acoustics GS-2, Genelec 8040, Yamaha MOX8 & MOX6, Truckloads of Classic Synths