One reason to add another VC server would be if you need the functionality that VC brings (DRS, etc), but do not have connectivity from your other office (which is unlikely). If you have connectivity and it is fairly reliable and not completely saturated, then you should use your existing VC server.
Even with a minimum VC config (2 procs and 2 GB of ram) you should be able to many more hosts than you describe above. Many large environments use one central VC server and manage hosts in other countries and other continents. At a former shop I had my VC server near Chicago and managed hosts throughout Europe, North America, India and even a couple in Puerto Rico which had a problematic connection. The amount of network bandwidth for most VC activities is minimal. If you will be deploying from tempates in one location to another or cloning between them, then you will probably have problems, but the routine communication between VC and an ESX Host is small.
So check with your network people if the connection is nearing saturation, maybe try copying a few files over to each location at different times of the day to test what kind of performance you see.
The only reason I can see is if you were looking to have both sites available to each other for using SRM for DR/Business Continuity.
