If you want a RTR from XTM, I'd say get the Mammoth ST. However, if you can afford the Mammoth ST Pro Kit, that's even better than the RTR ST. Good luck!
Here's links to both trucks:
Mammoth ST- http://www.hobbypeople.net/gallery/145619.asp
Mammoth ST Pro Kit (lots of hop-ups installed from the factory)- http://www.hobbypeople.net/gallery/145620.asp