Let me say it first, I am not here to offend or defend anyone, but I have to say something regarding these suspension stuff.
First of all, I don't like lowering cars and I don't think I would ever do it, but I will also never go tell people not to do it as long as they do it with taste.
Second, a suspension upgrade done by your local Lexus dealer will not void your warranty. That is that the TRD parts are for, they are designed to work with Toyota/Lexus cars without imposing too much negative effect on it.
Third, dropping the car by 1 to 2 inches will not hurt your drivetrain at all. Think about it, that is less than 5 degree of change. This is what CV joints are for, they are meant to tolerate at least 30 to 40 degree of bending without damaging the stuff they are connecting to. It is the CV joint that is going into the differential, not your drive shaft, so dropping a car does not affect that at all. If you don't believe me, get underneath the car and look at the input of the differential before and after the car has been lowered.
I think if you are enhancing the suspension by upgrading it to a coil over or a well designed kit, then it is perfectly ok. But please don't decide to cut springs and be cheap about it, because it will make the car look bad and it will definitely kill your suspension very quickly.