The NVIDIA GeForce GTX 1060 is still competitive at the sub-US$400 price bracket. It was originally released with 6GB of GDDR5X memory. A change to its product page on its maker's website now suggests that there are GDDR5X versions of the card.
https://www.notebookcheck.net/GTX-1060s-on-sale-now-upgraded-to-GDDR5X.343466.0.html