How many computers can a cisco 851 router support?

How many computers can a Cisco 851 router support? Have a network that consists of a 851 Cisco with 2 48 port switches behind it. Currently there are 30+ workstations that access the network and internet daily through the 851 with no issues, but plan on adding another additional 15 computers in the near future, should the 851 be able to handle it or should I look into getting something with a little more memory/processing power?