Well, you'r gonna need a very, very big internet connection before you're gonna reach the routers limits. It will be able to handle at least 10 Mbs. Search the forum, there have been reports that the router is able to reach 3 Mbyte/s throughput from WAN to LAN.
The number of clients isn't going to pose problems for you either. Your server will not be able to handle the amount of clients before your router does.