Given the amount of AAS that you're taking it is 'possible' gain less fat than someone not using AAS. And given that you're not even certian of your %bf or how much of what gear your using etc.... it's all academic. I was merely observing that at 15%bf you might consider cutting first, then adding muscle.
rex racer: The article that that info was taken from was a review article encompassing the last 10 years of research, including Forbes' own work on identical twins (therefore controlling for different body types and metabolism), as well as studies on other mammals (again using inbred animals to control for genetic and metabolic differences).
Hoffmeister: Of course the predictive equation uses absolute fat. I'm not sure how that differs from leaness?? This is a conceptual problem that I've noticed a lot of females have. They gain 20 lbs but are amazed that their PERCENT bodyfat has dropped. In reality they still have just as much fat as before (or even more), it's just a smaller proportion of their total weight on the scales comes from fat. Many bodybuilders also make this confusion when calculation LBM gains (assuming it's muscle) without factoring in the water component. Post competition is a classic example, but androgenic AAS cycles, high carb diets etc... also have this effect.
In summary, the last decade of research on large numbers of people of all ages, genders, activity level and body types (and other animals) indicate that it is easier to gain a greater % LBM if you start from lean, and you're more likely to gain fat if you 'bulk' when you're not already lean. The converse is true for dieting. 15%bf is not considered 'lean' for a male, but no one has done studies on AAS use for 15% bf males bulking (outside of the anabolic discussion boards LOL).
But since this is all academic and you're intent on gaining some mass with minimal fat on an AAS cycle, then the answer is train heavy, keep your protein intake high and avoid processed carbs. Keep the fats as clean as possible and incorporate some moderate cardio 2-3 times per week. Good luck and keep us posted on your progress.