Your ride comfort will go down. I would say much harsher. I assume you are going to keep your stock struts? The life expectancy of your struts are directly related to how hard you drive your car. Eibach springs may be the way to go.
One option for you might be the springs from Prodrive. They lower the car approx. 1.5 in. front & rear. They were designed to be used with the stock struts and are about the same stiffness as the STI springs. The quality of prodrive products is well known, as they have been building rally cars for a good while. I have british friends who swear by Prodrive parts.
I recently installed these springs, along with an adj. rear bar, and I have 17" wheels, and the car feels spectacular. I had the wheels first and they made a definite difference in ride quality (harsher), the springs made a lesser change in ride quality but a marked difference in handling. Much less body roll. I would agree though that this is about as low as I would be willing to take the car and is as low as you want to take it for performance/street driving and for comfort levels. My girlfriend did not notice a harsher ride after installing the springs.
They can be had at tirerack.com for around $300. Ask for Luke.