The Sage 200 extra Online version does not include Customer Relationship Management (CRM).
Since most companies in the 21st century need CRM or should be using CRM you will probably have to go for the on-premise version. I.e. installed on your server(s). This will add significantly to your hardware and licensing costs in addition to the cost of the Sage 200 software and services.
Interprise Suite has fully integrated CRM included as standard along with almost everything else you might need.
See our Sage 200 Price comparison