In reply to shingsowa:
I'm about the same weight as you and went for a snow plod in the alps a couple of years back in '75kg rated' shoes: It was a real slog, they didn't provide enough float and once I'd broken through the surface I was in upto my knees with every step, the mates I was walking with found it hilarious. Definitely spend a bit more to get some that are suitable for your weight!