Mr. VC,
Here is my opinion on a suspension modification I have made:
I had a 2003 Boxster S with 18" wheels. Standard S suspenion, stock Dunlop tires.
I changed to -> Michelin Pilot Sport 2s, Bilstein PSS9 coilovers, M030 sways, 7mm front and 21mm rear spacers. I dropped the car 2", and have an "aggressive street" camber.
I did not do an incremental change. The original S suspension and tires performed very well. It was the reason I bought an S! After driving it for 4 years, I wanted more sports in my car.
With the new suspension set up and tires, Shazzam! Roll is only apparent in yank the wheel go-kart type manuvers. On a mountain two lane with hairpins and 35mph curves, one can pull hard Gs with no washyness and that beautiful boxster balance plays right to the fuzzy limits of the Michelins. At higher speeds, I admit that the driver is the limiting factor to pushing this car. I have pulled many U-turns and headed back through a stretch of canyon trying to get brakes, apex, and throttle just right.
The real tribute, my wife likes the ride of the PSS9s and M030s better than the stock. (She rode my @ss about how uncomfortable the new ride WOULD be.)
Good luck with what ever your choice is. You can not go wrong.....you are driving a boxster!
Ike
PS: oops, I forgot the front strut tower brace.