Bilsteins are well regarded as the best shocks you can put on your Xterra, alot of people have been putting on Adjustable Rancho RS9000’s but the Bilsteins automatically adjust to conditions and provide a GREAT ride. If you’re planning on lifting the Xterra then make sure you get shocks that are going to be able to handle the extra travel without maxing out their extension. Shocks aren’t built to be limiting straps and will break if they have to be one.
Whatever shock you get be aware of which direction it’s mounted. Depending on the manufacturer they may go canister up or canister down. The reason is that some shocks have reflexive valves that depend on gravity to keep them in the correct position. The result is that if they’re upside down they may make the ride worse.