Seconded, non-podded Sternguard are a suicide team with no targets.
5 Sternguards with 2 Lascannons cost 160 pts.
5 Devastators with 4 lascannons cost 150 pts.
Your Sternguards in that set up cost a total of 655 points. I'm not sure what you want with them, but as an example
10 Sternguard with Flamer, Heavy Flamer, 3 Combi-Meltagun, Vet Sergeant with Combi-Melta in pod
10 Sternguard with Flamer, Heavy Flamer, 3 Combi-Plasmagun, Vet Sergeant with Combi-Plasma in pod
-> 640 pts
You could combat squad them, having one squad for
AT, two squads for anti-infantry and one squad for anti-2+
sv. Of course they will die gloriously, but should be able to do a nice alpha strike, as long as you also manage to pod the
TFC