The Saffire Pro 40 is a Firewire interface, featuring 8 of Focusrite's famous preamps, 10 analogue outputs, MIDI and S/PDIF I/O, plus ADAT connectivity for increasing your I/O count up to 20 inputs and 20 outputs. In addition to this (as highlighted in the video), all Saffire interfaces are also compatible with Thunderbolt connections using an appropriate adapter (sold separately).
A Focusrite Octopre is an ideal device for expanding the I/O count of the Saffire Pro 40, or indeed any interface with an ADAT input. The Octopre provides a further 8 channels of I/O, including 8 more of Focusrite's preamps.
The Octopre Mk2 Dynamic (as featured in this video) adds built in compression to the standard version, which can be used to help tighten up your recordings before audio enters your DAW.