So how much difference does adding 600 mg of testosterone, under a doctor's supervision, make to a trainee?
Over at A Workout Routine, there is a look at a study that compared no exercise vs. exercise, steroids + no exercise and steroids + exercise.
Steroids vs Natural: The Muscle Building Effects Of Steroid Use
Long story short: even with no exercise, additional testosterone can add muscle. With it, it no comparison with natural trainees.
This harkens back to the advice I started out with, by Stuart McRobert, who repeatedly made the point that non-steroid using trainees were ill-served by the advice of steroid-using routines. This article and the review it cites make a similar case. It's long but interesting.
Very Short Version: If you aren't taking steroids, get your training advice from someone who isn't, or trains people successfully who don't.