Be sure you read up on all the pros and cons about owning coilovers. In addition, be sure research the price of 19" tires, which are typically on the expensive side.
Here's a best practice when it comes to determining the correct wheel & tire combo for up-sized aftermarket wheels. This best practice is intended for a "plug and play" swap on a factory suspension.
If your factory wheels are 18 x 7.5 + 40 and wrapped with 245/45/18 tires. Just up-size to a 19 x 7.5 + 40 using the same or similar tire specs. Doing so will avoid wheel/tire rubbing. However, if you will be lowering your car be sure to factor in the reduced ride height to prevent wheel/tire rubbing.
Once you understand the tire/wheel sizing more proficiently, you will be comfortable using custom, and more aggressive tire/wheel combos.