Are the weap and armour packs really worth it though ? I guess it is only a couple 100 points.
Yes, Firepower and Aegis are more than worth it.
The weapons are mildly overpowered, but fun to use.
You get the geth plasma shotgun, which is pretty much
the perfect counterpart for the adept - strips most defences with ease, especially shields, which is great for making targets vulnerable to powers.
Mattock just decimates everything, with every class and every build.

You also get the phalanx pistol, which has laser targeting - a bit marmite, and I don't like using it with adept, but it has its place. Great at long distance.
The Aegis pack has kestrel armour which is the only other modular armour you can get (other than the standard N7 armour in the game). It looks good and has good stats - although you have to remember that part is not very noticable. The only thing which puts some people off are the lights all over the armour, but you can mix and match with the N7 stuff in game; say, kestrel torso plus strength boost pads, plus kestrel arms, plus stimulator conduits - just gives a nice variety, and more options to customise your Shepard.
Personally I'd get LOTSB, Kasumi, Firepower, and Aegis packs first.
Then get Overlord and Arrival later, if you don't want to spend all in one go.