which harness for head unit

[Bthurz]

when i go to order my new head unit for my truck it asks me wether i want the harness to use the factory amplifier or not if i dont how does it work? does the head unit do it or would i have to get an amp or what should i just use stock one? i dont have a sub so just for the 4 speakers

[zROCK]

Are you using factory speakers? Stick your head up under the dash and look just to the left of the sterio between the radio and steering wheel. Look for a black box with 2 connections on it. (it will be back more towards the firewall).

Personally i would just ditch the factory speaekers get new and run new wire. then no need for the adapter and sounds much better