I am a pretty good mountain biker, but i want to move up to bigger harder stuff, any suggestions.?

Moving up will cost you some serious money. Some of my friends decided to do downhill but those bikes are kind of heavy and the suspensions absorb all the pedaling energy so the displacement would be nothing in comparison to you hard tail bike. Try different scenarios. Deserts, forest, tundra like terrain. Forest is the best fro me cus all those tree roots sticking out of the ground make it really hard to handle. Good luck with that