both the powertrax and the aussie locker are awesome upgrades for traction as long as you arent doing some hardcore rock crawling or spinning huge 36"s. if you are mainly hitting trails, and driving through the woods, in the mountains, or in snow/mud they will be one of the best purchases you can make for your rig.
you can go arb air locker, or detroit for something more heavy duty, but seeing that you are looking to find a locker for cheaper than 300 bucks, im thinking thats not an option. i run a set of aussie lockers in my 03 sport trac 2wd with 33"s, and im not blowing smoke up your ass when i say this, but our sport trac mashes through trails, mountains and forests up in the high sierra mountains that my old 4x4 would have trouble in. ive had my aussie lockers for about a year, and they are holding up great with no problems, and they are pretty quiet.
we just got back from a weekend trip into the northern sierra mountains camping and driving through 50 miles of mountain trails and im positive that we would have gotten stuck at least a few times without the lockers. in fact, we also own a jeep wrangler jk and we find ourselves always taking the sport trac because of of all the space for our gear and its ability to get us in and out of the mountains.
as previously mentioned, just make sure you look up what diff you have, if its open then the aussie or powertrax will fit. if you have an LS, you will have to look at other options.
