[Advice needed] HW for mail server

[Anze Vidmar]

Hi!

I'm about to setup mail server (postfix, dovecot, squirrelmail, 
spamassassin, clamav) to help an existing mail server (exchange) in the 
same domain.

There will be about 50 - 80 users with mailboxes on this box. The 
machine will be Mail server only.

I'm planning to use some workstation machine with IDE disks for this 
job. The only thing that it's bothering me is how powerful must this 
machine be?

Any suggestions are welcome!

-- 
Anze Vidmar <anzevi at gmail.com>