I see nothing on the RRO page described as an "Extreme OME kit", so maybe you need to either provide a link or explain more about what your intent is.
Personally I think OME makes a great product and I've been very happy with mine (I drive a GV, not a Samurai), but I will tell you that they generally do not advertise their product as providing "X" amount of lift as you see on the RRO pages - their intent is to sell you a suspension system that will allow you to load the vehicle without it "sagging" when loaded, you'll note that their springs are rated as light, medium & heavy duty - this refers to the "additional" load you expect to be carrying. Typically you will get about 1-1/4~ 1-1/2 inch lift over the "pre-installation"height.
Please be realistic when estimating the extra weight as installing too stiff springs can make for a very unpleasant ride.
For what it's worth, you can email ARB direct;y and ask your questions there, I've found them to be very willing to discuss the OME products, and Low Range Off Road has been my vendor of choice for OME. The guys at Low Range will also be happy to discuss your needs, as I'm sure will be those at RRO.
When comparing kit pricing, don't forget to compare kit content as well.
