I bought the lip from D2 in Alhambra. The price was pretty good $800 plus installation and paint (totaling $950.... if I remember correctly). I'd shop around though, Sprewell San Gabriel is also pretty competitive.
From my experience, I wouldn't have D2's folks install or paint it.
My car came with BMW's sports suspension and with the lip, it does reduce the amount of clearance. You'd need to pay attention the concrete stop in the parking stalls where as with the stop bumper cover you didn't. Also steep driveways are now a concern as well.
Just a FYI. But adding the lip does make the car looks mean. :yup