Just wanted to chime in (disclaimer: new to FX) about spring stiffness.. stiffer does NOT necessarily mean better handling. Cars were designed to roll a little bit in the turns; the suspension geometry is set up this way. What you need is a compliant ride. Stiff is fine for perfect road surface, but if you hit bumps or imperfections and you get wheel hop (tire not touching the ground) you lose traction, and can slide/lose control. So long as Eibachs dont cause this problem when hard cornering, should be ok. But reality is that most roads suck.. a compliant ride will aslo be a better handling ride.
This was very apparent in my old M6 - H&Rs in this case were overly tight (especially in the rear) and once I almost lost control of the car while taking an onramp with a whoopsie in it at speed. Eibachs happened to be a more compliant ride, and after changing, the ride AND the handling was much better.
Also - shocks were designed around a specific spring rate. If you change the springs, and shocks arent matched, this will give you other problems. This gets very technical and nitty-gritty... so we will just leave it at that. I highly doubt most of us will really need to go this far in our SUVs!
My $.02: go with the springs that give you the drop you want, and most compliant ride.