We are down the storage rat hole, I'm not sure that is warranted now vs sorting out your current system, but if you are going to get a new PC you really should be on this new tech.
Samsung 960 Series have been replaced by the 970 Series. There is not much difference. The 970 Evo is likely what you want, but I'd buy a 960 Evo or Pro if they were bargains.
A M.2 PCIe/NVMe drive like those uses 4 x PCIe 3 lanes. You can get those from a dedicated motherboard M.2 PCIe slot or by sticking a $20-$30 M.2 adapter card into a standard 4x or larger PCIe slot. Like this
https://www.amazon.com/StarTech-com-.../dp/B01FU9JS94. As mentioned before you could even stick one of these in a spare PCIe slot in your current PC if you wanted to.
You are talking Dell PC again. I'm not so sure I'd go there vs. build my own PC.
Popular MOBO vendors are already shipping motherboards with three M.2 PCIe slots, and Thunderbolt 3 support... if you want to ever get those latest UAD interfaces you will dead in the water with that Dell and no Thunderbolt support.