With gpus supported by driver 470, this is a no-brainer
https://forums.developer.nvidia.com/t/ubuntu-20-04-not-able-to-run-6-7-monitor-setup-with-one-x-screen/200904/2?u=generix
Limitations are, the primary graphics card has to have enough memory for applications and output buffers, i.e. the 2GB of the 730 would be enough for about 6 FHD screens (rule of thumb: 350MB per FHD monitor).
Personally, I can’t recommend getting a Kepler based graphics card now, though. The 470 driver only has 2 years of nvidia support left now (distro patching probably longer), so its death is foreseeable.
My conclusion: If you can get a 710/730 real cheap, consider that but check out prices for a T400 (adapter cables might be needed, no VGA) and compare.