On my 23 se I snaked the wires right above the fuel tank down through the hole where the battery cables go into.
It took....10 minutes?
As for the power, I run BOTH my HDS7s from accessory switches. Not sure if that is the "correct" way to do it but it worked and was not a problem. The hardest snaking job I had on the parker was jamming on the wires into the tube running from electronics box up top to electronics box in console. Radar, power to the board, VHF, speaker wires, NMEA wires....all got jammed up.
Whenever I snake I leave 80 pound fishing line where I did it before so the next time it goes smoother.