Does anyone know where to find some kind of database that tells us what the 'optimum' amount of domains / emails / hits server setups can handle?

Is there a limit of domains or traffic levels for example that a server with this type of a setup:

Intel, 2.5 ghz, 256kb,512 MB ram, 80G HD.

Has compared to this type of setup:

Intel Xeon, 2.8 ghz, 512 MB ram, 1T HD.

Or does it depend on the type of scripting being used?

Regards,

Lee