the easy way to check if there is already a harness just unzip the rollbar cover behind the driver. if its not there than you will have to run new wires. if you do need to run your own wires i would say to upgrade to a larger gauge wire.
where to find a stock sound bar i have no clue. there are aftermarket soundbars out there, some not worth the money and some that have a fair price on what you get.