How large a server and how many?

So the question. How large a server do you need or suggest to run multisites. Certainly there are variables but what is the suggestion. When do you move to multiple servers? I've been told that we could end up managing around 3,000 blogs with a cap per of 100MB of disk space on this multisite.

Maybe the direct question first will this machine handle such a load?

This is the configuration of my server:
Intel(R) Xeon(R) CPU X3430 @ 2.40GHz quad core
6 MB of CPU Cache
1333MHz Front side bus
4GB of Memory
500GB hard drive
Apache version 2.2.17
PHP version 5.2.16
MySQL version 5.0.92-community
Architecture x86_64
Operating system linux

Would this be considered a good machine?
My plan includes 2000 GB of transfer per month.
I really want to make sure I'm on the right path before I get to deep into this project.
Thanks in advance for all of your opinions and suggestion.