Your ride quality on coilovers is going to go down if you're going to drop the car. There's no avoiding it, in my opinion.
I have never ridden on Teins, but I had many discussions with my shop guy who has been working on nothing but suspensions for 20 years. And that is what he's told me after complaining to him about my ride quality. After tweaking the preload and damping, I got my BCs pretty close to stock on full soft. But it's still not what it was on stock springs. On stiff damping settings, my organs get jumbled, and at higher speeds I've gotten tossed out of my seat and hit my head on the roof!
I know some people have mentioned how their ride quality improved with coilovers, but I find that hard to believe.