The TC line provides Bilstein quality at a lower price. Make your A3 Golf/Jetta handle the way that VW intended it to, before they softened the suspension to suit what they think are "American tastes."
The TC suspension is approximately 20% stiffer than stock, and is dimensionally the same, so it will not lower the car (it may be a little higher initially but will settle in).
Set includes 4 struts/shocks.
Consider also replacing your upper strut bearings and mounts as shown below, and you may wish to replace the mounting hardware as recommended by the factory manual.
Does not include springs.