Good luck in your intention.
The most popular proprietary/paid performance testing tools as for now are:
Each tool has free trial so you should be able to perform your own assessment, Loadrunner seems to be the most popular one.
In regards to free/open source tools, currently the choices are in
As aforementioned tools are free there is no problem to download and try out each one. However if your time is limited you can refer to Open Source Load Testing Tools: Which One Should You Use? guide.
Performance testing domain is very actual as it evidenced by Apple’s iPhone 6 Web Failure, outages of e-commerce sites on i.e. Black Friday, Xmas, NY, etc. when thousands of dollars is lost for each minute due to servers overload. Besides, due to work complexity, need to have experience in different domains apart from performance testing tool itself (application servers, databases, networking, etc.) makes performance testers more highly paid comparing to i.e. test automation engineers or manual testers.