How to select production IS for a project

How to select production IS for a project. The interfaces on the project are,

Credit Memo
Order Cancellation
Payment Capture

Msg Type: IDoc
Source: SAP
Target: Webservice call

There are 30-50 transaction per day and each transaction size cab be between 7000 bytes and 2147483647 bytes. Typically however we do not see requests larger than 2MB and average is probably closer to 10K.
We have TN and webservice calls in this project.

You will need IS, TN and SAP adapter.
For sizing, a basic box with 8G a memory should be enough.