Vogtland Fixed-Damping Sport Coilover Suspension are a fantastic all round suspension upgrade for a road car.
While you can achieve impressive improvements in handling, looks, and feel with a simple spring and damper combo, there are limits to what can be achieved. Because the damper unit has to fit into the same space as the original unit there's only so much improvement that can be made.
A coilover gets around this issue by coming as a matched set of spring and damper. This allows the whole unit to be wider allowing a larger surface area of damper inside.
The other big advantage with a coilover is they typically come with adjustable spring seats on at least the front units. This means you can finetune the lowering amount that you want for both looks and handling.
These coilovers use twin-tube dampers offering a smooth initial response to bumps in the road. This configuration also offers enhanced durability to stone chip damage.