The AX-10's are nice. My wife bought me the ARTR for Christmas, put in a Tekin fxr speed controller and motor (55T I beleive) and use a 3S lipo battery, much more fun than a lower voltage nimh; still goes plenty slow for crawling but you can goose it over obsticles with no issue. Used the coiled lead from the Walmart fishing section for weight in the wheels and can get it almost verticle.
Jason at Eastridge was a huge help with picking the speed controller and giving advice. Another good place to go is Action Hobby, Doug and Donette have always been good help and ordering stuff from them is painless. I'd stay away from PM Hobycraft, the big box store feel kinda rubs me the wrong way and their response when asked if they have a part is "sure, come down and check it out"; but most of the time when I'm looking for something specific and they say they have it, they don't. I'd rather support the first 2 mentioned.
If you're into speed the Traxxas Rustler VXL is pretty fun and fairly tough. The sand paddle tires you can get for them are pretty sweet.
I told my wife they were for my son, whom is 4. He can drive the rock crawler pretty good, but it might be a few years before I let him try out the rustler.