I would get a pair of the same dottybacks/pseudochromis and not a single of two different types.

pseudochromis will fight with anything that looks like it......if you are gonna get a pair....get a MATED pair.

AND........my porcelain (sp?) crab is AT LEAST the size of a 2nie.

Not at all small

In my 75 I have:
large yellow tang
blue sided wrasse
royal gramma
bangaii cardinal
purple firefish
green clown goby
2 chromis
2 clowns
red star
opie star
serpent star
fire shrimp
cleaner shrimp
emerald crabs
feather duster
2 urchins
various hermits
All seem to get along well and have lots of room. I would avoid the damsels even in a big tank. Peppermint shrimp have been eaten (they are too small) and I've heard that cucumbers can cause a problem if they die, leaving toxins in the tank. I may be tempted to get an angel but it might be too much. They were all added 1 month or more apart and i have a skimmer and 40 gallon sump to help with water quality.