I am facing similar issue, I maintain 2 laptops at all times for travel, am replacing older 17" HP w/ 2 GB card which performed beautifully w/ Chief V7. Currently have 17" HP w/ NVIDIA GTX 850M, 4 GB, 2 years old for Chief V9.
Also shopping the 4GB, vs, 6 GB, vs 8 GB, hundreds of dollars difference. Should I go for 8 GB anticipating that Chief will continue accelerating its requirements for next version? Any thoughts, or anyone with experience seeing the difference 4, 6 vs 8 in practice?