The 8930 is compatible with 64 GB of RAM as stated in the specs here. However the 3090 specs call for a 750W PSU minimum. And in addition this forum post has more information on the problems installing a GPU upgrade.
Hey guys, My rig is an XPS 8930 SE I9-9900K, GeForce GTX 1070, 16GB RAM, SSD. The computer is not for gaming, I use it for Visual Effects (Maya/Arnold render) and my idea is to use the full potential of the graphic card to make much faster GPU-based renders.  I intend to upgrade to 64GB ram and replace the graphic card with an RTX 3090. I'm wondering if this upgrade is possible and if the components are compatible. Do I need to upgrade the PSU as well? My hardware knowledge is basic and any assistant is appreciated. Best, Renato
XPS 8930 SE upgrades