Um, $600 only for the Truggy or the whole setup ( engine, radio etcc.. ) .?
If for the whole setup, sorry to say the X2 & the RC8T is out. They're kits and need to be built up, come with no engine, radio and servos.
If $600 is only for the Truggy, X2 all the way. Extremely durable, and handles like a dream.
Check out the Offical Thread, everything that you'll need or want to know about the X2 is there.
Heres the link..
http://www.rcuniverse.com/forum/m_7737298/tm.htm