.NET developer learning NodeJS, MongoDB, AngularJS, and ExpressJS

Question

I am a C # .NET developer, and the tools I use to build a web application are:

• SQL Server
• Entity Framework
• .NET Web API
• ASP.NET MVC
• HTML / CSS / jQuery

I read on AngularJS, NodeJS, MongoDB and ExpressJS, and it certainly looks like these Javascript-ish technologies, you can create a full-blown web application.

My question is, where can this leave me with my .NET stack management? I want to start using these new technologies and create my next website with them, however I am confused about whether I should completely get rid of the .NET stack, or if I have to add strength to these new technologies. NET where it might make sense. Here are some of my thoughts:

• MongoDB can replace SQL Server and Entity Framework
• AngularJS can pretty much replace ASP.NET MVC (since both are MVC patterns, since both will be redundant, I think)
• But when it comes to creating an API level, will NodeJS completely replace ASP.NET web APIs? or can i use them together? What will make the most sense (generally speaking)? Given that NoSQL databases like MongoDB have javascript-like syntaxes, do we need server-side APIs? Could the client (theoretically) talk directly to the database?
• Where is ExpressJS located?

I hope someone can help clarify how these technologies fit together. Pretty sure that many .NET developers who want to learn these new technologies have the same questions.