ah well, was staring at this thread for a while before realizing I just couldn't think of any new suggestions, I must need to just quit work for the day, sigh. I think you are on the right path with either a betta (OM47 and others have good tips on using them in a community, I don't know, perhaps should be a female, the betta people will know) or a Dwarf gourami. Dwarf gouramis, if you can get a nice male/female pair (or one male, 2 female trio) and have them live (there's some disease particular to the species that's been hitting them but its a hit or miss thing, so if you don't happen to get it right when you take them hom then its basically no problem from then on) are a great contrast to the tetras, cherry barbs and corys (if you had them.) They are larger-bodied, move more slowly and gracefully and the male of course has that stunning red/blue stripe thing going. The only downside is that being gouramis you've got to allow for a little individual personality difference that's unpredictable (but you get that with bettas too, by the way) and if your male as a result happens to be a bit nippy, he might nip at some other things in your tank or give one of his females a hard time, hard to predict. But I wouldn't let that scare you off as there's every chance of a perfectly docile and nice behaving one.
~~waterdrop~~