im 5 7" 135 pounds and just bought 2011 silencers in 169 cm. which actually measure up to be about 173cm. so you need the 176 anything shorter would be silly
Do you typically like shorter or longer skis? I'm about 5'11'' and would honestly reccommend the 181 or the 176. The 171 would probably feel pretty short if you normally like longer skis.