[whittsy]

10x Chaos Space Marines
2x Plasma Gun
Veterans of the Long War
Melta Bombs on Champ.
Power Weapon for Champ.

I'd be inclined to drop the plasma and take Melta guns, drop the melta bomb and VotLW and throw in as many bolters + CCW's as you can. This will allow you to shoot and charge with assault weapons and have a nasty volley of snapshots if someone charges you.