With a 1.5" drop, you're going to have to spring for caster/camber plates so your shop can get the front end alignment back where it needs to be.
As for the ride height, I have BBK progressive springs that dropped the car about 3/4", and I have occasional scrapes across speed bumps and even sections of uneven pavement (heavily ridged blacktop). At 1.5", you're going to have to make sure your exhaust system is tucked all the way up under the car and doesn't hang down at all.
As for rubbing, if your tires are the same diameter as the stock 17s, you should be OK. How does the width and backspacing compare?