I contacted various suspension vendors when I was shopping around...
When I contacted Icon, they responded stating that their coil overs use 650lb springs. 700lb springs were never mentioned. That doesn't mean they don't recommend them, but the person I spoke to said 650lb springs... No additional spring options.
Overland Warehouse uses 700lb springs on their HD 2.5" coil overs and 650lb springs on their 2.0" coil overs.
I contacted them and they were willing and able to outfit their HD 2.5" coil overs with 650lb springs if I wanted them to.
I've been told that the stock spring rate is anywhere from 525 to 585. I have not officially confirmed that anywhere.
All I can confirm is that I decided to go with Icon non-resi coil overs up front. My 4Runner is lightly modified and running 285 Revos. With this setup, the 650lb springs feel just about perfect. Stiff enough to prevent a lot of nose dive and soft enough to deliver a fantastic ride.
I spoke with the guys at Down South Motorsports when I ordered them... They had some real world opinions on the setup and recommended the 650lb springs.
If you add additional weight or prefer a stiffer/sportier ride, then 700lb springs might do the trick for you. The guys that are running 700lb springs seem pretty happy with them. I think one or two might have mentioned a stiff ride, but they had them cranked up to 3-3.5" of lift.
Hope that helps...