Indeed, there is an OME lift for the R51. Several guys on thenissanpath.com have installed it successfully. The major obstacles are a.) fitting the springs on the coilover shocks and b.) getting the alignment within factory spec afterwards. Unfortunately, it seems people have only been getting between 1.5 and 1.75" of lift, which in my mind isn't enough to justify the effort and cost.
As for the alternative, Calmini, that $1,600 is just for the drop-down parts; you're still looking at replacing the OEM springs and shocks when you're done. And I'm not sure I want to drive a 2005+ Pathfinder with 5" lift unless I widen the stance a bit.
I am looking at putting together my own lift using Rancho shocks, OME springs and Total Chaos UCA's. I'm hoping to get 2-2.5" lift plus gain 2" travel front and rear for about the same price as the Calmini kit. My goal is to mount 33" tires, which in combination with the lift will give me a total of 4-4.5" elevation, 2" extra clearance and 2" extra wheel travel.