Use those last 6 points to put a flamer in the Assault squad, not in a tac squad. You'll have the mobillity to use it in the Assault squad, and at 500 points you should be seeing a lot more troops and not so many vehicles.
You might want to switch the squad sizes on the tac squads, but that's pretty minor all things considered (I'd rather have the extra body protecting the more expensive weapon ).
(additional minor point - the entire Assault squad comes with frags, including the Vet: see the weapons section under the Assault squad entry of the 'dex. The frags on a power fist equipped model won't do you much good, he'll still strike last no matter what unless you choose not to use the fist)