We choose CRM for foreign business (SalesForce, ZohoCRM, SugarCRM, ...). What to choose?

Question

CRM

Dear users. There was a lot of information about the choice of CRM systems. But, since every business is inherently "unique", general advice on choosing large vendors ("vendor") is not always suitable.
In short, I would like to describe our workflow in order to choose the most correct solution, without unnecessary "crutches" and not overloaded.
1. Cloud service for receiving orders online (implemented through the company's website).
2. Further, the incoming order is calculated for a very long time (business specifics). In order to correctly calculate everything, we have written our own CRM system (application processor). Associated with complex pricing that only our system knows about. Just at some point decided to automate this process. As a result, the system evolved from an application processor into a full-fledged CRM system, but much "castrated" compared to advanced vendors.
3. The application is closed in the system, the client receives his goods, reporting documents are generated - an invoice for payment for the supplier (Invoice) and an invoice for payment to us in front of the supplier (Bill). All this is now done within our self-written system.
That's basically all the functionality at the moment and we are not satisfied with it. Yes, Megaplan was used to work with clients. It turned out quite wild - the data in Megaplan and in our CRM are not connected with each other in any way, we have to duplicate both there and there.
There were three options:
1. Add your own CRM to a state where third-party ones are not needed.
2. Rewrite our CRM for a more global solution and integrate (Force.com, Zoho Creator, etc.)
3. Leave only the request processor from our CRM, and put everything else through the API into a larger solution.
The first option is not suitable due to lack of funds for this. Still, for us, the development of the CRM is not a core business, and we cannot directly monetize it.
The second option will require less investment, but not much, and most importantly, it is not a fact that we will be able to rewrite our ticket processor with our "wild" pricing to other platforms.
We decided to opt for a more democratic option. Thus, we will take the best from our CRM, and we will link everything else through the API with some convenient cool solution.
And here the most important question arises - with WHAT ?! :)
We studied and watched a lot of different CRM systems. Here's what's important to us from the system:
1. Focused on international business.
2. Integrated with financial accounting / bookkeeping systems.
3. Ability to conduct marketing campaigns (including Survey).
4. Socially oriented (Facebook, Twitter, LinkedIn, etc.).
5. Work with foreign currency.
6. Good project management.
7. SSI is desirable so that users do not get lost in the variety of systems.
Alternatively, you can use several systems, but integrated.
We tried ZohoCRM, in conjunction with ZohoBooks/ZohoCampaign/ZohoInvoice, etc. It seemed pretty interesting. But the question arose about adding modules to the system in the future - how easy will it be? How easy it is to find then people working with this system and who could improve something.
SalesForce made a great sales pitch the other day. The advantage is that you can buy the necessary modules through AppExchange that work closely with CRM and you don’t have to worry (sort of) about integration. We think. But the solution is still much more expensive than Zoho.
Therefore, we turn to you, the users. Share tips or maybe experience in your companies. Probably many companies once faced such a choice. Surely there are many solutions.

Answer 1

In this regard, by the way, we are looking for a team or just people who have experience in implementing ZohoCRM and developing applications in ZohoCreator. Ready to consider all offers.

Answer 2

If you are still interested in SalesForce - contact me, I will help ;)