Dedicated server load question

Hi, We run this site in a dedicated server with few other small sites, My server specs is P4 3.0 Ghz wqith 1 GB RAM and 120 GB disk with Linux and Cpanel. I have 10 Mbps connection on that, i just wanted to know this config is enough to run this script for around 500 simultaneous connections? If the number of users cross 5000 will this server config is enough? Is there any guidelines for this or can any one in personal experience guide me|?

I think u need to have more RAM memory up to 4 GB and a larger internet CHannel if you want to support 5000 visitator in the same time.