AMD ROCm has come a long long long ways since last year, but you'll probably be happier not dealing with AMD's software.

I posted another comment with my experience with AMD 395+, I am overall happy and it's usable now, but it's only useful for models under 64gb of vram due to the active parameter counts on larger MoEs.

If you add 2x 5090s, do you actually need the base system?