Generally lowering 1.5 " is a good street setup without killing the shocks
and bashing your car on speed humps. Every type car is different, though, if you don't want your tires to be eaten.

Be aware that with some mfg's, their coils will ONLY lower your car the advertised amount, if you also buy their shocks....sometimes an
expensive arrangement.

I know how to calculate how much to lower a car, and can
even lower cars using stock coils/shocks, while retaining your ride
comfort, using your stock suspension adjusters, and not
eating your tires. Simplicity itself.-Bob