Odds are they would stiffen up the ride...but let's see good coil-overs run $750-$2000.00 and you think you can score a good set for $20? You get what you pay for.

First, I would inspect the car and make sure all of the bushings are tight and that the shocks and such are good. See a dealer if you need to....Putting performance parts on a semi-junky suspension = expensive junky suspension. I would assume your ride is a few years old. I'd fix the factory junk, if needed, before putting money down on aftermarket parts. No one likes to hear this, but it's so needed.

Next I would readup on springs, shocks/struts, and coil-overs get an idea of what each is first before you lay down cash on stuff. And then when you purchase be sure you are getting what you pay for. Ebay is not always truthful.....but shops like the www.Tirerack.com and www.Shox.com have been good to me in the past.