I am not that experienced with aggressive fish but I will relate what is going on in one of my tanks. I have 5 semi-aggressive Gourami's (very large) and one aggressive Cichlid (unknown species the owner of the local pet shop convinced me she was a Gourami due to the "spot" on her side). The Gourami spend most of their time chasing each other and trying to prevent each other from having any time off to relax or eat - they don't bite, just a lot of bumping and chasing. Totally left out of the game is my Cichlid who spends her day hiding in a tree trunk cave (so glad I bought that) or risked being chased and attacked constantly by all my Gourami's. She is more of a bottom feeder so she gets plenty to eat and defends her territory quite well - but what a lonely, stressful life.
It just seems to me that when you have so many tiger barbs and even plans to increase that number - then why not just have a single species tank rather than take the risk of injuring other fish you might try to add. The guidelines of what is supposed to be peaceful vs aggressive (and how aggressive) is not cut in stone - you might risk having a very unhappy situation going if you add fish even deemed "compatible"
Case in point, I have a single zebra striped danio - a beginner fish and one of the most peaceful. Technically he should live in a group, but he KILLED all his schoolmates by chasing the weakest one at a time until they died from the stress - then I was SHOCKED to watch him eat the fins off of one of my dwarf Gourami's (3x his size) because the dwarf Gourami was so overly passive. The Gourami died a day later. I do not allow him more companions and he's seemed to settle down without his "gang" - but I was SO close to euthanizing him.
Obviously get other opinions, but your numbers may be too high where you can't have a successful community tank unless you have room for similar/equal numbers and even then you may be inviting a huge amount of fighting and territorialism.
Again, an opinion of a newbie.