The barbs might work, just find them large...
I'd do either...
Columbians
Tiger Barbs
Buenos Aires
SDs
I'd do either...
Columbians
Tiger Barbs
Buenos Aires
SDs
Another vote for BA tetras. There are fast and hardy. They will eat live plants though but I doubt that is an issue with your tank.
Dollars or Balas will get way to big for the role you have in mind IMO. Your tank will be getting very full as it is looking at your current stock.