FWIW, these are my thoughts: For the Fischer RX-9 170cm seems to be ideal for your weight. Or put another way, I'm 180lbs and ski it in that length.
If you want turnier go with the Fischer RX-8 @ 160-170. The RX-9 is meant to be a GS type ski in with more versatile flex and dimensions to broaden its performance range. By virtually all accounts, Fischer has hit a home run with both the RX-9 and the RX-8.