Poor Tetras. :-( Most types of tetra like to be in schools of at least 6. I would definatly expand on those. It would make them alot happier and don't have to worry about Angel aggression. I remember my mom having angels in the tank with my tetras when I was really young and don't remember any fights between the two, but I wouldn't chance it.
Harlequin Rasboras should be kept in a larger group. If they are not schooling with the Tetras then they need more Harlequins to hang with. Forget about an Angelfish and get more of those schooling fish.
Lorazoo, My tank is a 30 gallon tall tank not a regular 30 gallon tank.
I'll get a few more bleeding hearts and rasaboras but I'd really like to get at least one angel. When I do get an angelfish I'll make sure to keep an eye on the fish. If there are any problems I could always moves some of the small fish to the empty 10 gallon I have.
you might have trouble with the angel when it gets bigger but if you insist on other fish besides the angel try a school of them and provide lots of coverage and know that when your angel gets bigger it will need a tank of it's own.
Edit:
Also,
if you insist on mixing an angel with something i'd highly suggest you get some good coverage .. A couple caves with tons of plants for cover.
Since you want something different than the usual community fish, why not try some drawf cichlids? Rams, cockatoo cichlid and kribs come to mind for this position. The only thing I would cation with these fish is to either hav only one fish, or have only one male with one or more females and have a seperate tank ready to move them to if they start to breed (almost all cichlids get very territorial when there spwaning).
A 30 gallon tall tank cxant really hold as many fish as a 30 gallon regular. It is really like having a 20gallon. The Angel will definately eat those rasboras when it grows up. You really have no cover either. I would really advise you to listen to everyone and forget the Angel until you get a larger tank. You already have a full tank with the Gourami and all of the other fish you have mentioned getting. To add the angel with everything else you want you really need a 55 gallon at least to make everyone happy and healthy. You will wind up having to move everything to the 10 gallon which will then overcrowd it. A full grown Angel will get to be 6-8 inches and will try to eat whatever it can fit into its mouth.
If you really want the Angel then forget the rasboras and the Gourami and just get a few more bleeding hearts and add the Angel last. And you will need more plants, rocks, hiding spaces for the fish.
You have to decide between having a full tank or having the Angel. They are too aggressive to crowd into a small tank with lots of other fish. I know they look all cute and small in the store, but they don't stay that way.