The stock Xterra has a good height compared to many other SUV’s coming out now but if you go offroad you’ll want more height to keep the belly from hitting the ground. The Calmini is arguably the best suspension lift you can get.
A quick word on lift types, there are two main kinds: the Suspension and the body lift. The suspension lift changes your suspension so that the frame and chassis are higher off the ground, the body lift just lifts the chassis higher off the ground the frame stays at the same height. Suspension lifts are limited with IFS because the control arms can only be at so sharp of an angle before they really mess with the geometry, anything over 3″ requires a lower control arm relocation bracket, which eliminates all clearance you gain by lowering the frame. Plus the steeper the CV axles the more stress on the CV joint. Body lifts don’t have any real benefit except allowing you to fit larger tires. Anything over 3″ can lift the body too high and the mounts can become distorted when the frame flexes.