All of these products feature 6TB Seagate hard drives and push that data along at blazing speeds thanks to Thunderbolt 2, making them "ideal for 4K workflows." If you edit 4K video and need some external storage that works as quickly as you do, then these could be your golden ticket.
The biggest of the bunch is the 8big Rack, which is the first LaCie Thunderbolt 2 rackmount storage solution. It rocks 48TB of total capacity and provides speeds up to 1330MB/s. At a more conventional size, you find the LaCie 5big (30TB) and 2big (12TB), both with Thunderbolt 2. Expect speeds of up to 1050MB/s on the 5big and 420MB/s on the 2big.
You might not be able to build your own Mac Pro on the cheap, but given how you have limited upgrade options, that Thunderbolt 2 port is really the best way for you to milk some performance. Expect all three of LaCie's new line to ship this quarter at prices yet to be determined.