Interesting and informative review regarding the 2005 Porsche Boxster can be found at: 
http://auto.consumerguide.com/auto/new/reviews/full/index.cfm/id/38222/
Automotive Consumer Guide had this to say about the 2005 Porsche Boxster Road Test concerning ride quality:  Firm control with tire choice a big factor in comfort.  18’s:  breaks, cracks, patchy pavement pass with little undue harshness.  19’s: ride is uncomfortably choppy on all but smooth roads.  Uneven surfaces induce more structural shimmy than in BMW, Mercedes-Benz, Honda rivals, but body flex more compromising.  I would appreciate feedback from 19" wheel/tire owners about their assertions.  Would you chose 19" wheels/tires if you had to do it all over again?