You guys are having tiger barb problems because you aren't keeping them in a big enough group... tiger barbs exhibit conspecific aggression only when kept in a proper sized group of at least six. Otherwise, they will live up to their reputation as fin nippers and all around jerks.
To the original poster: First, I am jealous of your torpedo barbs. They are awesome. They are selling for $25 each (wild caught) at my LFS.
So, first and foremost, what kind of loaches do you have? If they are a botia species, you should add at least 3 more for them to be happy. They do best in groups and you will see some funny behavior you won't see in a group of three. Look to add 3-7 more, unless they are clown loaches, and in that case you don't have the space.
For your BN pleco, if you get yours a BF/GF (depending on what gender it is) they will likely spawn for you. The males have more bristles.
It sounds like you are looking for more of a "centerpiece" fish?
Personally, I would just add another 10 tiger barbs, maybe of a color mutation, like green or red... and/or another 5 torpedo barbs. Another option, add some rummy nose tetras.
I like the look of colorful schooling fish over larger fish in a tank of your size... spend more money on the aquascaping--LOTS of live plants and driftwood.
You MAY be able to have angels with a school of tiger barbs of sufficient size, I would recommend adding the barbs and the angels at the same time if you go this route.