Like i said before, it's not going to be as simple as just 'bolting them on for a more aggressive look'. On a coupe body like a miata, you can do that, there's nothing to get in the way of it. But on a four door car like the P5, it won't be as easy. I would take them to a shop and have them explain what will need to be done to make them fit properly. They should be able to give you a more complete understanding of how difficult a task it will be.
Just looking at it, it looks like you'll have to mockup mount the fender, draw a line that follows the door gap, trim the fender into two pieces, one for the door and one for the fender. Then you'll need to add fiberglass to both to finish off the space where you cut the fender. Finally you'll need to paint and mount them on both the door and fender. Oh, and don't forget that youll actually want to cut the sheet metal of the car around the wheel arches so that the tires will have clearance you want. Also, if you bolt the flares to the back bumper, you're connecting the back bumper to the body of the car, so you'll never be able to pull that bumper off again.