For a better quality ride, it is generally important to get a balance between the shocks and springs. The biggest factor towards a smoother ride will be the shocks, but if the shocks are on the soft side you will need a stiffer spring to balance it out. Likewise if the shocks are stiff, you will need a softer spring to balance it out. Both the B8 and the whitelines are fairly stiff which is why the ride may be a bit rough for you.
Since you have already purchased the B8, the most cost effective way to fix that may be to switch out the springs and there has been a lot of positive feedback here regarding the Mountune/B8 combination (I believe there may even be a thread somewhere here about it). However, note that the mountune drop (while still quite nice) won't be as low as it is with the whitelines.
Another option, if you want to keep the same exact height, could be replacing the B8 with the Koni yellows set to one of the softer settings. Since they are adjustable, you can use some trial and error to customize it a bit as you like it. Although the Koni orange (Str.T) are definitely on the softer side, they may not be as highly recommended for the whitelines. Str.ts have a history of being less durable than the yellows especially for more aggressive springs, however if cost is a factor from what feedback I've seen so far, they should work and deliver a more compliant ride. Just keep in mind that they might not last as long.
Increasing tire sidewall does help the ride a bit, but it is usually not sufficient alone unless the roads in your area are fairly smooth (which I kind of doubt based on your post). Lastly, adjusting tire pressures can help a bit too, especially with the meatier tires on a 15" or 16" wheel but again it won't usually make the ride decent on it's own in this situation.
So I just recently swapped out my struts and springs for Bilstein B8s and Whitelines all around, thinking that would go a long way to solving my unhappiness with the ride quality in my '16... but it didn't. I've given it a week to settle in, and I still absolutely hate it. This is my daily and fun car (I drive all over the place for work, much less for recreational) and while I don't expect a Caddy ride I don't want to be tossed out of my seat on bad street or highway segment change. This is without a doubt the harshest ride of any vehicle I've ever owned; and it really puts a damper on driving it - which is a shame because there's really a lot to love otherwise. Im willing to try anything else, but would prefer to keep the lowered look if there's a good option out there.
So what have you all had success with on this front? Please, give me your honest comparisons so I can enjoy driving this damn car every day!
