Go for a set of Tecnomagnesium's 15x5.5, best looking replica on the market
and they are magnesium, hard to find though and they are getting expensive, they look to fat compared with the originals
15x6" magnesium replica :
www.furiani.de, these are nice but expensive, abouth 5800 Euro for a set of 4
In my opinion best buy are the originals, they are fine for roaduse and a good investment, for racing 15" steel ( saab, Ford mondeo,...)