Ya those boogie bumps are not cheap. But considering the price of other heavy duty truck offroad parts out there they are reasonably price and they do work really well compare to stock bumps. These goes on the front of a dodge cummins, the front end is stupid heavy.
http://www.prgproducts.com/shop/product/xterra-king-coilovers/Looks like Greg does sell rear kings with his valving, site shows rears are 750. You can always start with that then tune the shim pack to your liking. I have rebuildable shocks on both of my trucks, if you want to adjust your ride quality it's the best way to go.
I started the rear with a standard pack. Then went to get them tune with a flutter pack (softer on the small stuff then ramps up when you hit big woops).
If you get those shocks and you don't like the valving, I have the technology to rebuild them.