Ok, I don't know how many units you have built yet but I saw one of your Valks on the open painting comp so I know you have one of them.
So...
Your CCS
First platoon
Demo vets
Harker Vets
Valk
That should give you a decent amount of firepower and at 750 there shouldn't be too much armor and you can handle it with your demo team. And plasma guns. The valk will give you those pieplates you need and depending on who your playing you can mount who ever you need in the valk. On another note I think you would be 40 point short so you could add some more weapons to your CCS and maybe some heavy weapons in your vets.