Although they are slowly disappearing because of old age and attrition, I would say that the Samurai is the truck that you need to look at - especially if you want to wheel hard without spending lots of money.
A) lots of aftermarket stuff including SPOA kits, body lifts, steering solutions, gear reduction and 1.6L engine swap kits.
B) solid axle design can give you more clearance/flex for less money.
C) You can start wheelin' right away -- even stock they are pretty good.
The Sidekick/Tracker is more up-to-date engine-wise and can be modified incrementally too. Not that IFS is bad or anything -- it just takes a little more doing to give it proper ground clearance. I am sure that I will be harshly denounced in some circles for this stand, but I own both kinds of vehicles and also realize that, from a practical standpoint, someday I'll have to mod my Tracker once the Samurai gives up the ghost.
Either way, you'll be saving lots 'o money over modding a Jeep. And that's part of the Zukin' Tradition -- getting the most bang for the buck!
Hope this helps!