you should not have to keep any of those wires but most people choose to because there's no need to eliminate then they don't hurt anything being there and if you want to sell the car you can remove your audio wiring and it will still be functional in your case I would Trace down the negatives and make sure there are no wires going anywhere crazy but usually they just go to the frame and then to the engine block sometimes a small tiny wire going to a body panel nearby like in my truck but you probably have a newer car so I would try to trace them down to make sure basically the Big 3 is just upgrading the wires that are already there so once they are upgraded there is no point of having the smaller wires