Orion an Cirrus can be placed on the same server, but this is not the best set-up practice. We would advise to keep Cirrus separate for better performance.
Many Customers have Cirrus and Orion Installed on the Same Server without issue
To take load off this Server it may be best to have Orion and Cirrus DB's use remote databases. This means that the same SQL server can host both the Orion and Cirrus databases assuming the server is capable of handling the load of multiple databases.
If your Orion Server is running smoothly then there is a good chance adding Cirrus to the box would be fine, but there isnt an accurate answer on this as there are too many variables to consider.
You could try installing a 30 day Cirrus Trial on your Orion Server and if that goes well,
then migrate Cirrus to that box for good.