great list, definately playing to marine strengths atm. i would wonder, if DP'ing the sternguard in anyway, most likely to pop that armour first turn their down, i would be tempted to go for 5 combi-melta's, even if it means you only fire 3 first turn they're down, then next turn you have 2 shots, which could probably get a rhino or something.
good list, hope you do well!
good list, hope you do well!