My understanding is that the dealer can only deny you of warranty work if they can prove that the aftermarket part that you installed is indeed the culprit of the problem.
Blown stock shocks is a given. They're not gonna replace them if you slam your ride to the ground. I've already read about some owners blowing struts/shocks but they were using coilovers and dropped it crazy low.
I just installed a set of Hotchkis springs (1.5" front. 1 1/8" rear)
The front lowered more than what I expected. The rear is subtle.
Tein S.Tech springs lower 2.3" front 2.1" rear.
Eibach Sportline and Progress lower roughly at 2".
And then there's always TRD and Eibach Prokits at 1.25".
Also, I almost went w/ using H&R Sport springs at 1.3" front 1.2" rear.
Pics of my drop are here --->
http://www.toyotanation.com/showthre...threadid=16806