Hey all, ill give this one a go.
Johnjx, what kind of rig do you plan on turning this sidekick into? A DD/mild wheeler, aggressive wheeler with some road use, to and from the trail? What kind of terrain are you around? Mud, rocks, sand, snow? All of these things will help us help you come up with a good set up. (funny how that sounded)
My buddy has a 4dr sidekick he threw a home made intake on it, some new exhaust, 2.5" coil spacer with home made strut spacer, and some 28" super swampers and the thing goes pretty good.
Probably the thing that will make the biggest difference is your amount of traction. you can have all the Hp in the world but with no traction you are going no where fast. You can get lockers for the front and rear, which will cause all 4 wheels to get full power of the engine. Opposed to only power 2 wheels in 4wd (with open diffs)
Check out some of the other vender's, other than calmini...they seem to have some steep prices.
I have been using Lowrangeoffroad.com and they have been great so far.
Hope this info helps you out
Keep the questions comin man
Amilla