Ahhh, Finally a question I can show my knowledge and researched info.

Anything over a 1.5" drop on stock shocks will ride rough and prematurely blow your shocks within a few thousand miles.

A stock shock is engineered to sit in a certain spot when parked/not compressing.
There is a thick multi layered rubber and metal ringed gasket (shock piston) inside the shock that is mounted to the top of the shaft.
It is meant to sit in a certain spot (The Sweet Spot) when not compressing/dampening.
If you lower a vehicle more then 1.5", You are changing the Sweet Spot location and that will wear out both the inside wall of the shock and the piston, Not to mention there will be less travel clearance of the shaft to compress under load, and will bottom out the inside of the shock.
Bottoming out will eventually wear a dent or hole in the cylinder of the shock and break the seal.

Most if not all stock shocks have an allowance area of clearance before under compression, This is about 1.65" long.
That's why people that want a minimal lowering go with an Eibach Pro Kit.

There are also some good answers to any other questions you may have about suspension upgrading here in this link.
Eibach Springs - The Will To Win
OR
SHOCKS & STRUTS Motor - Find Articles
Or the best Article yet.......FTW
Howstuffworks "How Car Suspensions Work"

Aftermarket Shocks are designed to fit standard height cars and can work with lowered cars as long as they don't bottom out internally and become damaged. Unlike stock shocks,The inner wall cylinder of a Aftermarket shock is thicker, Longer, and the Shock Piston is made of a heavier duty material.Aftermarkets are not position sensitive so they will work properly anywhere in their stroke range providing they are not bottoming or topping out. Different vehicle suspension designs have different stroke travels but a good rule of thumb is that most vehicles can be lowered acceptably about 1 1/2 inches, beyond that the possibility of bottoming increases rapidly although some longer stroke cars can go lower. Most vehicles are equipped with bump stops to keep the shocks and springs from bottoming out. When lowering a vehicle be sure to reuse your bump stops as they are cheap insurance to avoid bottoming damage. Remember also that severely lowered vehicles typically also have a negative effect on suspension geometry, ride quality and handling, and tire and suspension part wear.

G/L with your decision
-Jeff