Dark Angels - 600pts

So my local GW Store is holding its first mini tournament. The challenge is to build and paint a 600 pt force in just 6 weeks and then take part in a tournament on a scenery heavy 4' x 4' urban board against any other forces that manage to qualify. I'm not actually taking part, but a friend of mine is and plans on a Dark Angels force which I've been helping him refine his army list. It's a fun challenge to try and come up with a list in that tight an amount of points that can conceivably take on any other force with a good chance of victory. This is what we've come up with thus far:

Dark Angels List - 600pt Challenge

HQ

Company Master - 90 points
Power Armour, Bolt Pistol, Chainsword, Iron Halo, Frag & Krak Grenades.

Troops

Tactical Squad I - 127 points
Sergeant with Chainsword & Bolt Pistol.
7x Marines with Plasma Cannon

Tactical Squad II - 127 points
Sergeant with Chainsword & Bolt Pistol.
7x Marines with Missile Launcher (Frag & Krak Missiles)

Heavy Support

Devastator Squad - 191 points
Sergeant with Signum, Auspex, Chainsword & Bolt Pistol.
8x Marines with 2x Lascannon, 2x Heavy Bolter.

Whirlwind - 65 points

Total = 600 points

I think it has plenty of firepower with a good range of Str/AP to take on varying targets. The Whirlwind allows the force to deny a cover save to a target unit, the auspex allows the Dev Squad sarge to reduce an opposing units cover save. The Dev squad is combat squadded with the sarge joining whichever half needs him most depending on the army being fought.

I would replace the Captain with a Librarian. You get more utility from the Librarian for less points. I would also reduce each squad size to 5 models and add another Devastator Squad with Missile Launchers or Plasma Cannons. The Heavy Bolters should really be in their own squad as they often don't want to fire at the same targets as Missile Launchers or Lascannons.

I don't have my Codex, but this should be about 600 points with some wiggle room for wargear:

Librarian
5 Tactical Marines
-Plasma Cannon
5 Tactical Marines
-Plasma Cannon
5 Devastators
-4 Missile Launchers
5 Devastators
-4 Heavy Bolters
Whirlwind

This gives you much more firepower than the first draft of the list.

Hmm, I think your list is lacking a bit in mobility. I would suggest reducing all the squads down to minimum and adding another Tactical squad, and swapping out the heavy weapons in the Tactical squads for special weapons. The Devastators are most effective with just one heavy weapon load-out, and seeing as the Tactical squads can handle enemy infantry, I would recommend 4 lascannons. I agree with swapping the Captain for a Librarian at this points level.
I would suggest:

HQ
Librarian- 65
Troops
Tactical squad- 80
Flamer, meltabombs
Tactical squad- 90
Plasma gun, meltabombs
Tactical squad- 90
Plasma gun, meltabombs
Heavy Support
Devastators- 150
4x lascannon
Whirlwind- 65

Total- 540

This leaves you with 60pts to play around with. That is enough to upgrade to the Captain if desired, although you trade Psychic support for a better statline and no other change in buffs, for 25pts. I would recommend putting any Auspexes purchased on the Tactical squad Sergeants, as they are more likely to get within 12" of the enemy and can benefit the army better that way. Some combi-plasma/flamers on the Sergeants would not go amiss either.

If you take Multi-meltas instead of Lascannons (not a bad idea on a 4' by 4' board) then you will have enough points spare for another Tactical squad or Whirlwind, which will either significantly enhance the scoring potential, or add another decent pie plate to the force.

Thanks for the advice guys, I've passed it onto my mate and there will be further alterations to the army list as a result of your feedback. Much appreciated.