Cyrus, the Silvia looks great. Go with it.
Benbsb, I happened to check out the M5 yesterday again and compared to the Norev Audi A6 and the Kyosho Mercedes Benz E class, the BMW is out of scale. More like 1:19 than 1:18. The paint on the silver one is horrible...terribly horrible. The headlights are all wrong and the grills are really wonky.