Well that depends on the bandwidth you will have available. Is it going to be an unmetered connection or will you have a monthly bandwidth allotment? For instance a 32man CS server packed 24/7 will chew up about 1.25 to 1.5mbps constant.
you would probably need a gbit port if you are really planning on running lots of busy servers, You would probably saturate the connection before you would use up all that cpu and ram, But I have heard different. I hear that the cpu and ram would overload before using that much. Guess would have to talk to someone who hosts lots of gamservers