Your question is confusing but I will give it a shot.
At the port on which 'your' server is connected every byte which comes by is counted.
You could buy more bandwith for the same server but thats often more expensive, most providers offer you the bandwith knowing that 50% of the customers will never use it. (same at dreamhost)
Further if your server is using 2000GB it's probably also using lots of cpu and cant handle more load (depends how you use the server)
This is a though question, it highly depends on how cpu intensive your applications are. A 200Mhz machine could setup several a thousand connections but actualy doing something on these connections could be a problem. Also the OS and applications used all are different.
The RAM is used for you applictions but could also be used for caching content. If you have only 1GB of data which is requested very often you could all load this in RAM so your Hard-Disk has an easy life. Another reason for lots of RAM are memory intensive applications like Java server pages.
www[x] is probably a different server but I'am not sure (I do not know how yahoo is setup exactly)
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