An accord saloon??? WTF??

The speaker wires are already there, just look on the underside of the rear deck and you'll see them there, next to each speaker opening. When you installed the aftermarket deck, i'm sure you hooked up rear speaker wires from the deck to the harness adapter. The plugs on the ends of the speaker wires (in the trunk) are kinda funky and wont directly fit aftermarket speakers, you can go to most auto parts stores and find adapters.