I am cloud setup expert and Linux expert(11+ years). I have a lot of experience setting private and public cloud using PAAS, SAAS and IAAS. Based on your requirement I would setup PAAS as service for your staging environment. And I will provide cloud/server support on time at very reasonable price as agreed by both of us.
Staging environment cloud can be setup on Amazon, Google cloud or I can suggest more reasonable cloud service provider as I have to continue support you, so I will take care of service quality of cloud provider while choosing them.
Also you are welcome to evaluate staging environment (PAAS) cloud setup, which I will setup free for 15 days by my own cost for you with cloud/server support. After that you can decide whether my cloud/Linux experience is appropriate for you or not.
Note:- Application/Server Security, backup/recovery setup and VPN access would be free.