You should only need the PAC ROEM-NIS2, 1m of extra earth cable, either heat shrink (to cover the soldering) or red bullet plugs (Male & female), Facia adapter & whatever headunit you wish. Then you need to connect the new headunits cable harness to the open ended wires on the PAC.
I put an ISO plug on my PAC then the Kenwood cable harness just clicked straight in. cable order = Bose - PAC ROEM-NIS2 - ISO Plug - Kenwood