Spring rates are really only part of the equation here, and while they are important when it comes to load handling, they're not the only factory. The ICONs use a 600lb-in spring. Both the ICON and Boss coilovers will sag a bit with extra weight on the front, though the ICONs will likely sag less due to their larger diameters and stiffer valving. However, the ICONs can only be set to a maximum of 2.5" of leveling, while the Boss coilovers can go up to 3", so if you have a particular ride height in mind, the Boss 2.0s would likely get you there more effectively with the added weight than the ICONs simply due to their wider range of adjustment. The Boss coilovers should be able to handle your application needs just fine.