Thinking I want to build a Knights list. Bought a knight last week...entirely motivated by the Knight stuff in Vengeful Spirit...

I'm thinking:

Knights

Errant (warlord)
Paladin
Errant

Marines (Ultramarines chapter tactics)

Captain w/power weapon, plasma pistol, meltabomb

2 x 9 man tac squad w/flamer

9 man assault squad w/sgt plasma pistol, 2 flamers
drop pod

5 man devastator squad w/2 heavy bolters, 2 flakk missiles

1849 points total

My only concern is objective taking...should I drop a couple of the assault marines and make the tac squads full strength so I can combat squad them? Should I drop the devastators all together in favor of a tank of some kind? Or should I consider allying AM instead for anti-air? Lot of choices to be made...

Comments? Questions? Criticisms?