Hi @w-repinski_1472 ,
Based on your initial usage, I think SQL Server Express will suffice. The ProGet database is basically a package metadata index, and essentially stores things like package name, version number, and a variety of things including the manifest file (.nuspec, package.json, etc). It's maybe a few kb per package, and you'll need 100k's of packages to even reach 1GB of metadata storage.
In your information you state that network connections are the bottleneck. I don't understand this completely in times when we have 100G cards, maybe I don't understand the scale on which ProGet is used in other companies.
The issue is with the number of connections, and a single server struggling with 100's of expensive queries/requests per second. Running "nuget restore" or "npm restore" will hammer the repository with 1000's of simultaneous requests, and many of those need to go to nuget.org or npm.json to be resolved. When you have multiple users and multiple build servers running these kinds of restores, then you run into load issues.
At about 50 users, a load-balanced / high-availability cluster starts to make sense. After 250 users, sticking to just a single server doesn't make a lot of sense (cost of downtime is expensive). Once you need a server cluster, then upgrading SQL Server would probably make sense.
There's a big cost difference between a single server and a server cluster - in part the ProGet licensing fees, but also managing a server cluster is more complicated. Some organizations prefer to start with high-availability right away rather than worry about upgrading later.
hope that helps clarify!
Best,
Steve