Depending on the system, we have been using Dell R500 series which is now at R540. We have found that depending on how many users are accessing the system, RAM can be an issue if you are using server-side motion. It depends if your cameras are supported to use camera-side motion. 16GB should be OK if you are splitting the cameras across two servers.
It can be a tough sell. It depends on how easy they want the system to be. Dahua is not easy, Spectrum is. Those that don't want to spend money, get Dahua and deal with the quirks.
For the workstation, we generally custom build the machine. For 90 cameras, get a really good CPU as DW doesn't support GPU acceleration and a dedicated GPU is really for more displays and running the GUI. 4K cameras on Spectrum take a lot of CPU. However, Spectrum will automatically scale to second stream but will mostly run the CPU at max.
Your server choice should rely on your PC knowledge base and who you want to support your equipment. You will generally pay more for DW provided servers but if you have an issue, there is only one vendor to contact for software and hardware and cameras if you get their cameras. It depends on the risk you want to take.
Our experience has been that Network Optix has taken care of almost every bug we have reported. My big complaint with DW has always been their lack of a ticket system. Network Optix uses a ticket system and it works well. We have dealt with their support, but I have experienced too many issues with support where even when I get through, the issue isn't known or can't be resolved quickly. That being said, contacting support is the last thing I ever do and I work through the issues and try to document and be able to reproduce the issue before reaching out. I'm not calling/emailing because my mouse doesn't work.
NOTE: If DW has finally started using a viable ticket system such as Zendesk, that's awesome. I haven't tried support in probably over 4 months, so there may have been improvements I'm not aware of.
