I found an old article run in Super Chevy comparing stock leaf rear to the Quadralink. Here's the link in two parts:
http://www.superchevy.com/technical/...oit/index.html
http://www.superchevy.com/technical/...ing/index.html
I don't recall any article comparing front subframes etc.
I also agree that a modified stock suspension can get you close for less. It all depends on your goals and budget. If you have the budget the DSE stuff will definitely help make your car handle tons better while allowing for a civilized ride.