I have a Yamaha RX-V683BL and I would like to plug four 8ohm speakers into the zone 2, left and right, that's 2 speakers to the left plugs and 2 speakers to the right plugs. This will be for the outside patio. Is this safe for the receiver ? Do I need a speaker selector switch ? Inside the house I will be using the rest of the plugs for the 7.1 surround.