On the '06 bilstein's will be the best bet on the back, however, Rancho also makes a stock replacement in the 9000 series which is good. There are a lot of options out there for the rear, you just have to find something the right length and then hope they're valved right for the X's weight.
Front shocks... not many options. You could go with the stock bilstein from the OR package or Rancho now has the RS9000 adj. available as well. The other option is the Radflo height adjustable coilover which will run you about $900 a pair but are the best things out there, hands down.
Someone mentioned having a Bilstein coilover for the front but until we see pictures I'm calling BS!