I run mine the same and just take a combi melta. You don't know how long they'll last under return fire and if they get charged whatever it is will probably kill them, also you'll be lucky to get the charge which is the only time BAngels
Tac squads are anything special in combat, so for those reasons I stick with a cheap and cheerful combi melta and don't take power weapons like other have suggested.
2 melta shots and a krak grenade out of no where is great