I think you'll be better off with a good cable. The cheap cable will break on you while off roading. But I would change out the back deraileur for a good one. That will help more with the shifting. The forks may fail after a while, because the seals on the shocks are weak. MTB hubs are built tough, even the cheap ones. I don't think they'll give you much more problems then a good set will. It's the rims and spocks that will take most of the force on drops and jumps. So they will fail way before the hubs will. You will want to keep a close eye on the chain as well. The cheap chains will strach and then jump off the gears. Then will be doing face plants.