Stocking levels should be about 12-14" in that tank in my estimation. Therefore you are really just about there I would have said (barbs 1.6" each, endlers 1.75" each, Gourami 2").
Depends on your water parameters and water change regime - if they are OK and you change 25% a week religiously then you might be able to add some more. You might get away with 3 pygmy cory's?
As to the Gourami, either one on it's own or groups of 5/6 or more.
1xTrigon 190
3 Clown Loaches,14 Cardinal Tetras,8 Rummynose Tetras,6 Cory Trileneatus,6 Hatchetfish,4 otocinclus,1 SAE,1 Bristlenose,, 10 amano Shrimp, 1 pair Apisto Agazzizi. 3 Blue Discus
Anubius Barteri,Crinum thianum,Limnophilia sessiflora,Rotala rotundifolia, Echinodorus Blehri, Ech. Parviflorus,Ech. cordifolius, Ech. Tenellus, nymphaea lotus, Hygrophilia polysperma, Microsorum pteropus,Lilaeopsis brasiliensis
1xRekord 60
Blue Lobster, Flash plec
2 Anubias Barteri, 1 Microsorum pteropus 12 litre tank - 3 Glass shrimp, 4 japonica shrimp 1 Anubias Barteri, Riccia, Eleocharis acicularis Coming Soon - Bluedave's 5' Bullnose Marine Divider (Watch this space!)