The headlight switch is a good feed because you will not have to cut a splice, just lug the end of the radio feed wire and use the screw terminal on the headlight switch....

Jim

__________________
14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles