I'm not sure about the gen of your ride-but for the street I would NOT recommend a 19" wheel. You best take a hard look at this and the width as well. Offset is going to be an issue too.
As to lowering-I use nothing but Koni shocks. You can go with one of several ways-Neuspeed Sport or Eibach Prokit, progressive rate, springs or Skunk2 or Ground Control Coilover sleeves and springs to match how you drive.
The real issue is what happens after you lower the car. ALL 5th gen preludes suffer from a rub problem in the rear if lowered more than 1.3"-simple to fix. The fix is to cut away the small nub of plastic on the inner edge of the bumper cover near the bolt that holds it to the fender lip.
You will also want to consider Camber kits. This is determined by getting the car aligned and comparing the stock numbers to the ones after the drop.
Hope this helps you. You have more q's-drop me an e-mail.

Hey Irene-how is your coar doing now?