I got a very over-packed 4in. pot of Rex begonia at HD for $5 a while back. I turned it out of the pot and was able to divide it up into 10 smaller plants. As of this year, I have about 6 large pots of that begonia around the yard, they are beautiful!
Highly recommend dividing if the pot is crowded, they take very kindly to it. In this pot, 3 small divisions filled a 9in. pot in about 2 months.
Lower left in this pic are the most recent divisions of divisions of that first little pot.
