OK....first thing you need to do is go into the suspension section of this forum. There is a sticky you can read through. Then if you have time read through as many threads as you can about each setup.
I'm on my 3rd setup. From what you have said so far, springs/shocks are suffice. Unless you have $$$ to spend, then you could consider coils. But from what I've read and my personal experience, they're overkill unless you want the ability to raise/lower and/or make it really stiff for whatever.
On E90's, eibach pro kit looks perfect for you. You are concerned with the rear..but remember, if you buy either kit, it will not be the same drop all around. When you buy the kit, you specify whether you have sports pkg or not.
You should look at the H&R cup kit too....
In the process of restoring an 07 335i