^Wow - no way.
First, what's your skier ability? It sounds as though you're a relatively big guy, but this is your first set of twins. I'd normally say for someone your size 176 is a bit small, but hey, if that's your preference, than fine. I'd say that the 181 Hazmat should be fine for you as it is a semi-wide ski and the double rise shouldn't make that much of a difference. If you're uber uber advanced and were riding 176s for kicks, maybe then you could go as high as ^this, but I think you'll be fine at 181. I'm 6'0 ft and 185 lbs and I ride 185 Scratch BC and 180 Salomon SPK and they're both fine.
So yeah, skier ability will help, but overall you should be fine with 180.