Crab spider armor, wolf spider armor, and other questions
Yes, the armors are stackable. Yes, this means you will have more resistance than otherwise. The resistance numbers aren't all that impressive, especially on the wolf armor, but then again it's a passive and certainly won't hurt.
What powers you chose to get or stay away from will depend on what your goals for the build are. There's considerable variety for crab builds, though the most popular approach seems to be "AOE damage machine" - which is certainly effective.

Iscariot's Guide to the Tri-Form Warshade, version 2.1
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Wolf Spider Armor provides 3% S/L resistance and 2% Psi resistance which is pretty much useless. It also provides 2 points of mez protection which you probably don't need as long as you have fortification (Fort + Crab armor gives 12.3 points). Unless you're a PvPer I wouldn't bother with it (if you've got a spare power slot take Recall Friend or something).
Thanks guys for responding. I'll stay away from the wolf armor. I just read that fortification is a good damage resistant power. Will that power go hand in hand with the crab armor? If so, what are the numbers for fortification? Thanks
base Res +15% to S/L and +25% to all other except psionic.
My Soldier just hit lvl 24 yay me lol. Going crab all the way. Here's my questions: Are crab and wolf armors stackable? If that's true, does that mean that I will have double the damage resistance? Also, what powers should I choose or stay away from? Thanks!