I also think that taking out a loan to modify a car is a bad idea. You're better off putting aside some "play money" from your usual income and saving up. But anyway....
Ground Controls are fine and should work fine with your AGX. Just know that lowering past 1.5" voids their warranty.
The S2000 silver color is nice...on an S2000 because of the lines of it's body. I'm not so sure that it'd look nice on a civic but that's all personal opinion. If your current paint is in good condition, I'd just save the money or sell the car and trade it for one in the color you want.
17" wheels are too big for my tastes but if you really like them, go for them.
20% tint seems pretty dark but that seems to go with your tailights so if you're happy with them, yeah, keep them.
The amount you can drop your car depends on your wheels' offset, the springs or kit you choose, and even whether or not you cut your bumpstops. I'd say you can probably safely drop from 1.5-2.0" if you wanted to but it's hard to say. How low do you want to go?