Put bios in achi mode, remove all other drives till install is completed. This makes sure the boot files end up where they should instead of off on a storage drive.
No reason you can't upgrade memory. Ram is cheap these days.
7980XE on Asus ApexVI
Zotac 2080Ti
Intel 900P
2 x Samsung 950 Pro
EVGA 1600W
Alienware 34"
Samsung 28" 4K