Upgrading CentOS Server Hardware?

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http://serverfault.com – My (postfix) mail server currently runs on an old PowerEdge 2650 and it badly needs a hardware upgrade. I would like to put it on an 8 core (3rd Gen) 2950, but have no idea how to go about changing hardware. Do I have to install CentOS on the new machine and then figure out how to get postfix/mailman/ldap all working on the new one? Is there any type of information on how to do this? I have no idea how modular linux ACTUALLY is. If I install a new version of CentOS 5.4, should I technically be able to copy over /var /usr /root /home /etc and have the server work exactly the same but on the ne (HowTos)