Well according to your bodyfat estimations and body weight increase, if you do the math you gained ~23-24 pounds of lean body mass.... in 2 years.
Sounds like you're doing a pretty good job if you ask me, 12 pounds of lean mass per year is incredible progress. It seems like you're looking for a GDA to be a game changer with an uncalculated and poor nutrition plan. While a GDA will help some, it will not be too significant if you don't have a grasp on a healthy diet, calculated macro intake, and proper training.
From your stats, you're making great progress. I would try to clean up your diet and figure out how many calories you need to consume to gain 1 pound per week. You can just wing it and expect a GDA to save you from fat gain. You're going to gain some fat during a bulk, we all do. But if you're smart about it and you're training hard, you can keep fat gain to a minimum. But as far as Slinsane goes, I would say its worth trying. The price can't be beat for what it has to offer.