It looks like that kit adds 2" to the front and 1" to the rear - it's a cheap way to fit bigger tires on your JK.
You may want to look at either a cheaper option (no spacers in the rear - just enough of a spacer in the front to be level) or a more expensive (better) option - Currie makes a JK levelling kit that also allows more suspension travel if you add long travel shocks.
http://www.tellico4x4.com/product_info.php/cPath/3601_3603_3613/products_id/32593Currie also offers the front and rear kits separately, so you don't have to touch your rear suspension if you don't want to.
In my
limited experience, I've found that there seem to be three steps towards being happy with a mod to your Jeep.
#1. Decide what you want your Jeep to do that it currently doesn't. Don't mod just because someone else thinks you should, or someone tells you that you can't wheel on 32's.
#2. Do your research - determine what's available that can get you that performance. A good question to ask is "Why is Brand X $500 cheaper than Brand Y?". Odds are that the answer isn't just the brand name...there's probably differences in the components.
#3. When you purchase, don't cheap out. You don't need the biggest, baddest, squishiest long arm coilover desert racing rig ever built...but if you buy cut-rate suspension components you'll end up regretting it. I don't know anyone that's expressed buyer's remorse over buying Currie, Clayton or OME suspension parts.