The cost starts compounding once you go over 2 inches!
I think 3 is a good happy medium, for this you will need
springs
shocks
caster correction (either offset bushes, radius arms or drop boxes, I will be getting the latter when I do mine)
longer lower rear trailing arms or the coils can rub on the shocks
extended rear sway bar pins (+ plus front of you just use bushes, pretty sure you cant run a front sway bar with drop boxes)
longer brake lines
All this can be had for under 2k delivered. I plan on getting the superflex kit
http://www.zordos4wdsuspension.com.a...d=49&Itemid=53
Best to get new panhards, draglink etc which I will end up doing but not essential to begin with