I just got a few pairs of ExOfficio pants to wear at Moab next week. I chose a couple of pairs of convertible pants (legs can zip off) and one pair of air strip pants that have massive amounts of mesh in them to keep everything cool.
Yes, a bit pricey, but they feel pretty good and their shirts have always been very effective for me in hot weather.
1993 Suzuki Sidekick 4-door
4" lift, air lockers front and rear
Shrockworks winch bar, w/Warn 6K
T-case gears, sliders, rack, etc
and a 97 Lexus LX450, just bought, all stock