performance coil springs

[Angel 24]

So im looking into buying some stiffer springs. Right now im running the original springs but i cut about 1 2/3 of the coil off to lower the car's front about 2 3/4in. I've been running it like that for about a year now. Feels good with some soft shocks. Smooth ride. Problem is that when ever i go over a speed bump, it almost bottoms out in the front, sometimes actually hitting the bump stop. Like its too soft. Obviously because i cut them. I want something of a variable rate like new cars. I hear good things about the 620's. But the other day, i noticed that NPD has some 550's. Both of these coils offer a 1in. drop. So im definitely going to be cutting them for some more. I have a coupe with a 351w in it. Its a daily driver so i dont want it to be too stiff. I upgraded the front sway bar to a 1 1/8" and in the back i have 4 1/2 mideye leafs. Ill be adding a 7/8" rear sway bar soon. So what would you guys recommend for my set up? Thanks guys.