To add to what Jason said - ensure that you do a Proof of Concept on the tools that you evaluate on your own system against your application to ensure that you can verify that your requirements are met.
I have not failed. I've just found 10,000 ways that won't work" --Thomas Edison
Also, Mermathon, it would help if you would specify what it is you are trying to do with the tools. Are you doing unit test? Functional testing? GUI testing? Load testing? Each has it's own set of tools.
Your question is akin to this: "I am building a house. What is the best tool to have?"
Thanks for ur responses. im a beginner in testing field and recently cleared my ISTQB foundation exam to start with. there are myriad of information and i donno where to start. what to learn next. why .net testing? Could please suggest what to start with if im goin to learn any tool or how to proceed through.