The Wilwoods also fit over standard wheels, there's a pic somewhere showing it. Another thing to consider is consumables, replacement DS2500 pads for the Wilwoods are approximate 1/2 the price of the the OEM fitment.
That combined with the new kit being 2/3rds the price of just a second hand pair of calipers does mean it should be considered.
That's correct. The Superlite uses bigger, much thicker discs and the calipers are a lot bigger as well.
They go nicely behind 15" Team Dynamics Pro Race 1.2s