The MD1200 is an enclosure that will present the drives to a host controller on a controlling computer. You'll likely want an HBA like a LSI/Broadcom 9205-8e or 9300-8e to control the drives.
The NX3200 is a network attached storage solution meaning it should have some sort of server inside, though the EBay listings may have removed the motherboard. It may not have the right backplane to connect to another computer.
Edit: Just to be clear, the MD1200 can connect to any compatible SAS HBA, doesn't have to be the Dell branded one. LSI/Broadcom makes the most common SAS adapter chips and are in cards from a ton of companies, as well as first party adapters.