How long can I go?

i have a 95 civic, with 215/40/17 tires. I have coilovers, and i lowered my car so the fender gap is about 3-4 cm in length, and the tires don't rub.
I want to get lowering springs instead of coilovers becuase my crappy coilvers are so bouncy. so my question is how much drop should i get for the lowering springs to get the same height i have now?

Thanks for the help~

Eibach Pro-Kit (1.6" drop)
Neuspeed SofSport or Sport (not sure)
Sprint (1.5 or 2.5" drop)
I have Eibach Sportline with stock rims/tires and there is almost no wheel gap.