Identify technology solution for consulting practice

Develop a technology architecture for a small consulting practice.

At this stage I only want the architecture. I do not want anyone to build a sharepoint site or a portal or anything else. That may be part of the solution but I don't know until I understand the full architecture.

At the moment I am trying to understand what potential suite of products can "work together" as our business grows from 5 to 20 staff. I do not want any bespoke systems so that we are not tied to a particular freelancer in the future but understand that there will be requirements for configuration for any solutions proposed.

What we need to be able to do
- track time
- manage projects
- communicate with team and external (Outlook, Skype?)
- Knowledge management
- store and share documents (backup/security)
- customer relationship management (and automate proposals / statements of work)
- manage business finances

Our website is currently in development

We want to use excel (and other office products including outlook) rather than Google suite as excel (and powerpoint) key for delivering our services. Should this be office 365 or desktop?

The number of staff is 5 currently. Grow up to 20 staff.

Please provide an overview of what solutions combined could provide us with the key functionality required (that can "talk" to each other) and pricing. We do not want a bespoke solution but off the shelf products.

The objective is to be simple and cost-effective

In terms of output I would expect a picture and 1-2 page of description pricing of "off the shelf" products recommended
Thanks