Yeah, pretty much.
You won't need the cage either.
There is a bag of short screws that comes with the SPH-DA120, use them to attach the brackets that were used to attach the OEM HU to the centre console which is also used to anchor the centre console to the car.
Just attach to new HU (three screw per side) and then mount the bracketed HU into place, don't bother screwing it to the centre console plastics. It also makes for easier tidying up of wires and future access if you want to change the setup (like rip all the Bose gear out and then run RCA wires etc. to a new amp)
Don't forget to run a grounding wire from the Pioneer loom to the bulkhead, you can also ground the handbrake wire to this to bypass, this then allows watching vids on the go (for the passenger of course)