Ummm.... good question, even though it has been covered before, and you have tried the search function.
The general school of thought is that it wont hurt the superstrut joints at all when you lower it as the geometry of the suspension arms are sufficent enough to allow for this. This doesn't mean that you can completely sack the car out and still be ok, but that a drop of around 50mm at most will be good so long as the vehicle gets a proper wheel align ment after installing the springs.
The other school of thought says that if you change your springs and lower your vehicle, the super strut joints will wear out quicker. But these people also don't realise that the quickest way to wear out any part of your suspension.... is to drive on NZ roads.
There are several different types of springs to use to lower your car, each has different characteristics and good points and bad points. Every person, especially on T.S, will give you a different opinion on each spring/ brand etc.
For your vehicle: (drop heights are only examples, each vehicle is different)
King Springs: 30mm or 50mm drop - most people say they give a poor ride quality
Dobisport: 30mm - Some people say they are a little too soft
Lovells: 25mm or 50mm - Not a bad spring, but sort of hard to come by.
Whiteline: 20mm or 40mm - Good ride quality, some springs are hard to come by.
TRD: 25mm - Good handling, available at a resonable price through Mr Revhead
There are others but these are the main brands. Its up to you which brand you go for.
Cheers

Your Opinion Means 1/16th Of Stuff All To Me So Dont Bother Arguing With Me About It As I Just Dont Care.
Thank-You.