If I were you I would def go bigger unless you feel more comfortable on smaller skis. At your height, I was skiing a 169 and I felt like I wanted more. Look at the 169 and possibly the 174 depending on your personal preference. Just for reference, how old are you though?
dude my 169 2012 domains are 3 cm taller than my 169 2011... and my 2012 domains are almost as tall(1-2cm less than his) as my friends 177 4frnts clicks... so yeah they're definitely bigger than others skis(I know that the fact that they're some rockers makes them a bit bigger too)
If you think you're an advanced skier, I'd go for the 179. At least go for the 174. I would hesitate to go with anything shorter than that at 5'9. I'm 5'11" and also about to be 17, 140 lbs, and I'm on 181 pipe cleaners and they fit me perfectly.
i have a pair of 169s and i'm you're height/weight, the size feels right. I've only had a day on them (today in fact) and they're nice to butter. It remains to be seen if I can get used to narrow skis having only really liked fatties in the park before.