I looked into this not long ago.
Spoke to the guru Fred @ YozzaSport.
Choose sportlines over prolines any day (My opinion).
If your not going to change the shocks, don't go for any lower than Sportlines (about 20/30mm drop). The shocks will FUBAR with any more than that. Also Sportlines aren't aggressive. Makes the car sit perfectly, stops it looking like a 4x4. Handles a lot better aswell. Best mod for the money I've ever done.
In fact your not far from Fred. Take a trip down, you won't be disappointed.