If your 16V is going to be your track car, I would seriously consider getting rid of the SLS, not only to save weight, but it would also allow better tuning of the rear suspension. If I'm not mistaken the Sportline and the 16V already have the same roll bar and springs, so there's not much to be gained by putting a Sportline kit on a 16V.

For racing, look into adjustable rear links and camber plates for the front and back, along with lowering springs and sport shocks. For roll bar upgrades, the W124 bars are the cheapest upgrades for the 16V but there's a number of people developing thicker bars specifically for the W201.