My office of 25-30 or so people has a server that does file depository, DNS, DHCP, NAT, email, VPN, ssh, and runs services for PCLaw, Amicus and several other obscure law programs and it is just a 1.4GHz Pentium (3 or 4), with 1Gig Ram, 80 Gig SCSI 10,000 RPM RAID5, with a cd-rom and floppy. Very basic, but it gets the job done and is never overworked. It's all a matter of the number of tasks the thing is running, and for what purposes.