Depends on many questions to assess the load.  For example, will all 100 users be actively using Sage at the same time?  What will they run in Sage?  Is Sage 300 to be delivered to users on a LAN, remote desktop, web or mix? 

I assume 50 users on LAN and 50 on Web, all users accessing Sage 300 at the same time, and all modules will be used all the time. 

OK if all concurrent then that's a large load.  The MSSQL database will be OK if correctly configured.  However, I don't know how/if the Sage 300 applications will handle it.    

Sage 300 supports Client/Server setup and can access from Web. However, there are different user experience using either so it is a complicated process. I will suggest you to work with a partner to smooth this process. 

My suggestion is to check the installation and administraion guide first, and setup a test enviornment. You can have a separate Sage 300 server and Web server so they handle different user access. MS SQL should be on another server depending on how powerful your servers are.

Noted Thanks. I cannot have test environment because don't have the right hardware. but I will suggest the separated servers setting to them.