I believe Tool Pants is referring to Porsche not recommending running 18" wheels on '97 Boxsters. Apprently, Porsche had to reinforce/strengthen some parts in order for the Boxster to run the larger/heavier wheels(?). But then again, if you're running lighter 18's than the stock 17's then I guess that logic goes out the window.
Both H&R and Eibach have a line of springs that will drop 2". Their "normal" sets will drop about 1". As for application specific to the Boxster I don't know. I wouldn't drop 2" even if I could unless it was a specific track car that won't see much street use. Your camber is going to go way negative and unless you have camber plates to bring it back closer to "normal" spec you're going to see a fair amount of tire wear. I'll be dropping mine 1" with Eibach springs. That's as far as I'd go for street use. 2" is way too much.