Voice coil size is just one way of seeing through the exaggerated claims made by manufacturers of audio gear. As the technology currently stands, a 2" coil should handle up to 200W, a 2.5" coil up to 300W and a 3" coil between 350 and 500W. There are other factors involved apart from voice coil diameter, but I wouldn't be confident using anything smaller than 2.5" (unless it's in multiples) for bass backline. Your TKS 112 has a 2.5" coil, by the way, Funkshui.
(I'm talking bass drivers here, not compression drivers)