I'm about 170 pounds, give or take a few pounds.

I don't have much to go on yet, but I know I'll be looking at a Giant Rincon, Giant Boulder and a "Diamond back", that the seller told me are "older", heh. Not a lot of information to make a decision, but will the first two Giants hold up? I don't plan on doing anything to crazy other than singletrack trails with rocks/roots/sticks/holes in the path. Kind of impossible to take a guess on what the diamond back is.