Um--dwarf gouramis don't really do too well together unless they are female--which I've already stated are hard to find. You can get male/female pairs of the larger gouramis. Also, aussie you might want to watch that combo of two d gouramis and a betta, sounds like a combo that will lead to at least two dead fish.
That was going to be my question about gouramis, so it's only the dwarfs that males can't be together? Bigger ones can be in male/female pairs? Do they breed easily though? I really don't want to deal with fry.
You can keep the dwarfs with one male and a bunch of females, but it is harder to find the females. But you can get m/f pair of the larger species of gourami--the females are more readily avalible. Some people have had success keeping more then one dwarf gourami together, but I have not.
If you can find them you could try Honey Gouramis, they are smaller than dwarfs and have a great personaility. I went with a male and female, the female has a dark stripe down her side, and the male is constantly changing colors. Their throats turn deep blue and their fins bright yellow when they are ready to mate. Just a thought, a 30 isn't THAT much bigger than my 20, and it would leave more room for other fish.