12 guage would be the best. Although 16 guage would be OK for shorter runs, I still wouldn't use 16. Use 14 guage instead, especially if you want to save some money on speaker wire. I would also recommend banana plugs. It makes it easier to change speakers or move things around, especially when you need to get to the back of your amplifier. Banana plugs also minimize or eliminate the potential of the stranded speaker wire making a short across the amplifier outputs/speaker when you are making/changing connections. If you don't use banana plugs,you should at least tin the exposed end of the speaker wire with a good lead-free solder.