Personally, I think the Smith machine is useful to do chins, barbell shrugs and maybe to hang your towel on. That's about it. It forces your body into an unnatural groove which really puts a lot of stress on your knees. It also uninvolves the hamstring, which stabilizes the knee-joint. Most leg presses are shit too, although you can find good ones, e.g. Hammer Strength. If your gym doesn't have a power rack, find a new gym. Even the crappy commercial gym I go to has one power rack. In the meantime, I'd say drop the leg extensions in favor of leg curls. Also, at the top of your routine it says 'Legs, Calves' but you're doing no exercises for your calves. Throw in some form of standing calf-raise(Seated calf raises only involve the soleus.) That's just my take, however.