Need some help load testing my New Streaming Server :P

I had 20... I was hoping for more. The resources I have (CPU, RAM) will be able to handle many, many users beyond that because I barely got a blip on that front. What I don't know is how many I can have before the bandwidth craps out and my neighbors get angry. The server has about 10 to 12 other VPS's on it. I'm serving 7 sites myself from mine but this is the only one that gets significant traffic. It's like a gamble because I really have no idea what they are using except by CPU which averages about 3% (2Xquad core xeon processors if I remember correctly) , they could all be simple backup servers with no use for all I know and I have the full power of $200 dedicated server...