i put some 2.5" on mine and it made a world of difference. they are fairly easy to install. there are 3 types, plastic, aluminum and polyurethane
plastic: cheap, but have been known to break after a few years. cost 70-75 a per set
aluminum: expensive, but bullet proof, never sear down. i have heard rumor tho that they squeek after a while. 100 dollars a set
polyurethane: my favorite, they are strong, dont squeek, they are a hard rubber so they act like a second bump stop too. cost about 90 a set.
if you have any questions or need help installing them just post up i'll follow through, they are pretty simple tho. i would highly recommend renting a spring compressor from autozone (it's free) the can be installed without, but it's a PITA.