switch is basically like an expansion port for your router. If you ran out of port then get a switch. However there is simple switch and manageable switch. Manageable switch allow you to control how much bandwidth is going to each port and which port you want to monitor. If traffic congestion is your issue then get a manageable one. If not just get a simple one and have the router QoS do the work. Go with 10/100/1000 seeing how our internet bandwidth is increasing rapidly. Faster the better. As for 16 ports? I found this
D-LINK DGS-1000-16 Port Easysmart Gigabit Switch Desktop or Rackmount (Rackmount Ears Included) - D-Link - DGS-1100-16