I'm on the heavier side (250lbs - need to lose 30 lbs.) and starting the weight loss process. I'm confused as to which amino acids to use. I'm currently taking 3 density per meal and 5 post workout out, but am wondering if I should be taking mass aminos instead until I get lean. Also, with Mass Aminos and Density available, what's the purpose of Muscularity? I guess I'm a little confused by the different amino acid products and the purposes of each.

I would check out a previous post here in the supplement section by SWade. It answers the question of Mass vs. Density very well. Read it HERE.
Muscularity is going to contain the three branch chain amino acids plus some insulin regulating ingredients. Research shows that the BCAAs, leucine, isoleucine, and valine, not only play a huge role in muscle maintenance and growth, but they may increase the amount of fat you'll lose. For these reasons, Muscularity works well in a fat loss type diet, not only for muscle retention, but aided fat loss.
I would continue to use Density as you are and possibly add in Muscularity if it is in your budget.
CR

Thanks, CR. I did read SWade's post. Do you think Mass Aminos would be more appropriate if I were in a muscle building phase, or can I use it in stead of Density and Muscularity as long as I'm mindful of the calories, OR, is there really no substitute for Density and Muscularity. All these different amino acid supplement choices are quite confusing.

Density is the superior amino acid formulation for fat loss and muscle retention. I would stick with Density and Muscularity while fat loss is your main goal.
When you goal changes or you focus more on adding lean muscle, Mass would be a good choice.
CR