Personally not worth installing a spacer lift on anything with over 35,000-40,000 miles. Springs are already starting to sag, so a spacer lift is only a band aid fix to lift it, many have used them but have finally went full spring in the end anyways.
As far as money a spacer lift cost about the same as or more than what two springs will cost, you have to buy new longer rear shocks and really should buy new front shocks so in reality you are only spending 160-170 more for two more springs over what a spacer kit cost!
Back in 05 when I first lifted mine it took me two months to save up and buy everything, but that lift lasted me 100,000 miles, so for the money well worth it.
Now just for S&G's lets compare
full OME kit springs and shocks from jeepinbyal.com is 750.
now spacer lift is 160. plus you add in new front shocks for 300, new rear shocks for 192 and you have 652 in a spacer lift. ( there are cheaper shocks for the front and rear out there though) So both ways either spacer or full spring you can save.
As a matter of fact I have 2 OME front springs ( brand new ) sitting in the garage right now waiting on a buyer for 100 plus shipping ( save 60 bucks right there
Also if buying I would only buy from people who have supported the KJ lift markets over time like
www.boulderbars. com and
www.jeepinbyal.com
If you want to know more about what works or don't come on out, I've done 20 KJ lifts to date and helped with more than that.
Oh and the if you are not going off road "a spacer will be OK for the street" is BS totally. Don't you want a better ride and great handling every day ?