spec_r,
MS SBS 2003 and MS Server 2003 are completely interoperable in terms of Active Directory and Domain features. SBS 2003 is basically a small business targeted verion of Server 2003 that's got some nice add-ons bundled into it like SharePoint services.
To compare Versions of SBS 2003:
http://www.microsoft.com/windowsserv...s/compare.mspx
Note on this page that a Microsoft recommends Server 2003 rather than SBS 2003 for "size of business = 75 or more".
To compare Versions of MS Server 2003:
http://www.microsoft.com/technet/win...s/compare.mspx
There is a rather complex matrix of features/capacity issues with all the versions of MS Server 2003. You may not need enterprise - Standard R2 might do. If you can get SBS 2003 R2 for less than MS Server 2003, it might be worth the cost savings and extra features as your basically on the cusp of recommended capacity for your company size.
Both of these product comparison link should clearly spell out all the differences between the various versions of ALL these 2003 products.
Be careful about SBS2003 in terms of any current or future apps you might need to run. Because SBS2003 comes bundled with MS SQL Server 2000 (used for the built-in SharePoint Services), there are some 3rd party APPS which DO NOT work on SBS 2003. I'm personally in such a bind now with the small medical practice where I manage IT. The medical software vendor pre-bundles their package with a limited licensed copy of MS SQL Server 2000 - which conflicts with the built-in SBS version of SQL 2000. That said, I'm going to have to dump SBS2003 and migrate to MS Sever 2003 (probably R2 Standard as Enterprise is probably overkill for my environment).
Again, SBS 2003 and MS Server 2003 are completely interoperable in terms of Active Directory and domain services so it really doesn't matter which one you purchase.
Hope this helps.
- John