NATAN666 said:
you can achieve the same results with a spring and shock combo... but they would have to be perfect.
This is probably the most important aspect separating coilovers like Teins or JIC's from spring and strut combos like Eibach/Tokico. I used to run H&R springs with Koni Yellow struts, and it was very easy to tell that the springs were not well-matched to the struts--the lowering springs shortened the effective suspension travel more than the stock-height Konis could handle, even when they were adjusted to the full firm setting. Then I purchased a set of Tein HR coilovers used off of ebay. Even with who knows how many miles of abuse, the Teins felt so much better than my 20k mile old H&R/Koni combo...
Eibachs may be better matched to stock-height struts since they are closer to stock ride height than the H&Rs are which should in turn provide a more balanced ride. However, unless the struts and springs are designed to work together, or the struts offer adjustable height spring perches and a nice, wide range of damping adjustability, you'd be hard pressed to find a combination that will provide the matched ride of a well-engineered coilover system.
Even then, you're looking at at least 2/3 of the cost of a coilover system to take a chance that your springs/shocks will play nice together...
This is just my experience. Maybe I did it wrong the first time; maybe I should've invested in some stiff Bilsteins to go with the low H&Rs...but at the time, that would've put me $700+ in the hole for a non-adjustable setup, so I went with Konis. If you just want to get something that looks nice and handles ok, spring/strut combos are the way to go, but if you're going for perfection, a coilover system is the only way to do it.