If you enjoy coding in C# and working with the .Net framework I'd recommend that you have a look at WPF. WPF is a great GUI framework where you can do just about anything - and also make it shine! WinForms might be easier to get a grasp on, but I'd say WPF is more "future proof". Another positive thing is that WPF is really similar to Silverlight, so if you handle WPF well you should be able to write Silverlight applications too - if that's of interest. Please don't bother to learn MFC.. I can't believe there are many that is using MFC today for other reasons than that they were using it before, and didn't get an opportunity to change..
There are a lot of good jobs out there for .Net programmers, so being able to handle some GUI framework in addition to C# and general knowledge about the .Net framework will be worthwhile.
When it comes to your points about being able to "deliver some performance like archivers, cryptographic algorithms, codecs" this really shouldn't depend on your choice of GUI framework. This kind of code will be writen in layers outside of the GUI layer, and will typically be bound to the GUI. With WPF you'd write your e.g. cryptographic algorithms in C# in some class independent of the GUI layer, and then the View written in WPF would bind to C# code and get its answer from here. However, if you used WinForms you'd still do the same thing, and the performance relies on the algorithms - not the GUI.
When it comes to getting started with WPF there are a lot of questions on SO helping with this. So you should find good help with a quick search.
Good luck!