ASI Service Center is tightly integrated to Sales Order in several ways.  The most obvious is that when you create an invoice from a service order, the invoice is in Sales Order Invoice Data Entry or Sales Order Shipping Data Entry.  You can also use Sales Orders and Invoices to send out demos or loaners which are then tracked in the Demos and Loaners subsystem, will appear on the Open Demo/Loaner Report, and can be viewed in Demo/Loaner Record Maintenance.  Finally, Service Center adds new fields to the sales order and invoice tables that you can then add to forms and reports.