[JanS]

I tend to avoid Tiger Barbs since they make anything else you can add to a tank so limiting.

I don't think they would do well in the same environment with Gourami's who are slower moving and they would make a good target for the TB's.

I think the Rasbora's would be the best choice of the 3 considering what else you have in the tank. You may be pushing the limits for a tank load though, so I'd keep an eye on your water qualities if you do add something.

 

[JanS]

thaerin, the reason yours is considered less overstocked is because most of your fish have a smaller body mass (with the exception of the Bristlenose).
Even though Dwarf Gourami's only reach a length of 2 or 3", their bodies are almost as tall as they are long, so that really increases the load in the tank.