I have a question on top of my matrix setup. Has any one integrated VoIP? I am trying to bring all communication in house.

I recently setup a full matrix server. What I am currently worried about is my server. I am currently shopping for a used dual Xeon server. I am hosting close to 40 docker containers on 2 1 liter PCs with very low specs. I would love to bring it all in house to a single server with a separate NAD which I do have currently holding 60 terabytes of storage space.