You could go with a M.2 PCI-e SSD like the
HP EX920 with read speed up to 3,200 MBps and write speeds up to 1,800 MBps
I prefer a disk in the middle of the pack with good speed that won't break the bank like the
Inland Professional 512GB with speed up to 1,500 MBps and write speeds up to 900 MBps and in real world task you might not see a different in performance between those speeds.