Can someone help me, I know nothing about them.

Right now I have a HPI Savage and a T-Maxx (just sold the booger).

What would I need? I want the best of the best, and how much would that cost? I got $400 to spend, if I need more I can get more.

What is all the stuff I need?
How fast would it go?
Are they fun?? lol

I know alot about the Savage and T-Maxx, I don't these things could be any harder to learn.

Thanks in Advanced.