... and because some package is provided in the MAIN repository does not mean its stable, either. I run amanda and have been doing since 1998, the version that is in the main repository (2.5.0p2) is 5 years old and crashed my 5.4 server (and another server I look after part time voluntarily). I currently run a self compiled 2.6.1 and never looked back (this includes all of amanda's clients).
I don't think you understand how Red Hat (and thus CentOS) package things.
The version of Amanda in RHEL 5.4 and CentOS 5.4 is indeed 2.5.0p2-8 (the -8 is important) and is not yet 6 months old, much less 5 years old. When Red Hat packages RPMs, they often times back port security patches and bugfixes.
As to why it crashed you server, I can bet that there are other config and software changes you have added "by hand" that may have caused a problem. We have a few CentOS 5.4 systems running the standard amanda packages without any problems.
Ian