Hmm, thats a lousy bias. I didnt know xj's were so off balance.
I run FOA's on my current set up. They are "okay". I'd be more inclined to recommend fox, but obviously you are looking at the dollars and cents.
Valving for what you have and what you do will be fine with light medium/medium. Anything stiffer will make for a bad ride in a rig that light.
Spring rates. For a good semi go fast and very good ride keep your rates around 175/250 in the front, and 200/250 in the rear. If you are planning 5-6" of uptravel you can run dual 14" coils with those rates and have minimum to no spring unload at full droop. Its important that you dont have spring unload with FOA's, else the lower spring retaining cup can fall out.
You can run triple rate but that would entail tearing the shocks down and reassembling with a tender spring and a triple rate slider. King has the best tenders if you are looking at tenders.
If going triple rate, use a 12/14" spring combo.
Unless FOA has changed their sliders, buy some Fox dual rate sliders and use those. The FOA's are to small, and do not allow your second rate to engage properly.
Im in langdon. If you would like to stop by and check out the FOA's on my rig over a coffee, feel free to get ahold of me.