Christian,
your 2001 sport more than likely came with a D35 for a rear axle, and a D30 for the front axle. The D30 front axle is the better of the two axles; it's the D35 that is the true weak link in the drive-train. The D30 is a pretty stout axleshaft assembly and will easily support a selectable locker which is most often recommended over an automatic (always engauged) style locker, even with 33" tires. The D30 in the 2001 is a 297X u-joint (someone correct me please if I have this incorrect) and much stouter than the 260X used in the Yj's. The limited slip style lockers are not always going to work when climbing over obstacles --- LSD's are somewhat more effective in sand and mud trail conditions. Long term --- limited slip devices wearout, apparently, after only a few thousand miles. I like the ARB locker, but there are many other selectable lockers to consider. In regard to the D35 rear axle, I would recommend not wasting any money on any upgrades for it; replace the D35 with a stouter axle as soon as possible. The D35 has thin tube housing, marginally acceptable axleshaft strength, and non-floating c-clip assembly; 33" tires are possibly pushing the envelope for the D35 rear axle design strength. Welcome to the wonderful world of Jeeps! That moniker "It a Jeep thing . . . " is all about building a capable 4x4 trail rig.