the mear fact that the car is lowered has nothing to do with the ride quality.

i would say it's either, the spring rate, the shock valving (setting), and the stiffness of the sidewall (tire).

spring rate, there isn't much you can do about unless you know who makes a compatible one and you know what rate you currently have.

shock valving there isn't much you can do about either unless it's adjustable, in which case you can make it softer.

lastly the tire stiffness you have some control over by lowering the tire pressure a pound or two but not too much as you might damage your wheel/tires if you hit a pot hole