Based on my car, I would guess yours will drop 2" to 25" to the fender lip. My hangers only have one mounting hole in them and the instructions on the site only show one hole so I don't know how far apart they are, but if they are not centered in the bracket, then I would guess the lower hole might lift the car somewhat.
Lowering the stance lowers the center of gravity and the car has to handle better. Also, if you can see the spring on my car-it is pretty flat and this definitely improves handling. It is not quite zero arch but it is a lot flatter than the springs that were on the car.
My car was a 318 car that someone had stuffed a 440 in, but, had not changed anything on it...springs, torsion bars, nothing. Oh, did have the obligatory set of air shocks on the back.
I had already picked up a set of upper tubular control arms so I bought rear springs, rear and front sway bars, the RCD-Bilstein shocks, bushings, shackles, etc. I bought PST 1.03" bars and rebuilt all the suspension then when I pulled the engine to fix all the frame rust, I added the FFII rebuilt steering box.
How much better is a subjective question. I would say, the harder you drive the car to the limits, the better it gets. If the car is just a driver and you are not autocrossing, racing, etc., then you will probably be quite happy with the improvements given by your current parts.
I have not yet added frame connectors to mine, but, I would definitely go that direction before replacing any of the parts you have already bought.
I have been using Bilstein shocks for years and consider them a really good bang for the buck even costing more than the KYB's and the IAS. I have only had one set of the IAS and thought they were pretty good, but, they did not have the life of the Bilsteins or the ride control, but, they were good compared to the usual replacements.
Sounds to me as if your current stuff is a good start and I would spend my money on connectors, or whatever else you need to begin with. You can always upgrade later if money is burning a hole in your pocket