I just went for 32GB, as it was cheaper that way (8 sticks 4GB for 20$), 8GB FBDIMMs are quite rare where I live (I prefer local junk shops for these old server RAM sticks)
For the GPU, 2 options for ultimate upgrade:
A flashed AMD R9-280x can get you boot screen
A Nvidia GTX980 no boot screen, and need Nvidia web driver installed before actually installing the card.
I let loose the R9-280x deal, and got GTX680 in stead (35$), as I already has the original 7300GT for boot screen when needed.