Greg,
I wouldn’t go with the readon cards, their performance is sub par typically (look at results in video linked). A sub $400 AUD graphics card whether professional or gaming would be underpowered for any ArchiCAD model of complexity as it would not have enough memory, you really need 8gb of memory to have any longevity, you can pick up an EVGA GTX1080 off eBay for about $500 AUD ( the 1070 is a significant step down in performance).
As a critical piece of your work system I wouldn’t skimp on hardware as it pays for itself many times over and of course it is a tax deduction
Scott