I'm glad i stumbled on your thread, I also had a 5 gallon tank, and put 3 gourami's in it! They were very happy once the cycle finished (overstocked with 4 Gourami's and 2 Guppys.) 3 Gourami's were very happy in there, especially enjoyed the live plants I bought at petsmart.
I recently also started a 20gal in the living room, cycled and stocked it with an Opaline Gourami, 2 more guppies (4 moved out of the 5 gal to cycle the 20 gal), and a Golden/Sunrise Gourami, which didn't survive the drive home very well I suspect, as it didn't last very long.
Having the 20 Gal in the living room the guppys were very dull, so I switched the 5gal Gourami's with all the Guppies. The move went very well with one exception. The Opaline Gourami seems to be very aggressive towards the other 3 Dwarf gourami's. He seems to chase one or seems to be nipping them, though I don't see any signs of actual damage to scales or gils. I'm not sure if they are playing, but it seems to be more mean like bullying.
Their diet is freeze dried bloodworms for now, next payday I'll get more flakes and probably brine shrimp for them, but they don't seem to fight over food.
I'm considering removing the Opaline, but it's quite attractive once it relaxes and turns white again. I'd even thought of getting 2 more, and trying to breed them. But that would probably just add bully's against the dwarfs?