Gene,
RAID is you friend. When you glance at your server and see that one of the drives is blinking RED after blinking Green for months and months, your heart will skill a beat [or race]. You log onto the machine and it says "Yeah Drive 3 is toast! But, I'm fine, just toss in that new drive sitting in the box up on the shelf and I'll rebuild the array on the fly. Don't forget to buy a new spare -KKTHKSBY " ... or words to that affect.
Workgroups are effectively peer networks since there is central domain controller.
For small practices MS has released a version of the Small Business Server 2011 Essentials that gives you the core functionality, and no requirements for paying per user CALS (up to 25) Costs ~ $700
