They do make tall 30 gallon tanks, but they aren't very wide, so you sacrifice a lot of surface area. A 29 gallon tank might work, too, as long as it's 18 inches tall.
If you get the idea of angelfish out of your head, then you can do a whole lot with a 30 long. A 30 long makes a great Amazon biotope with maybe 2 pairs of german rams, a whole bunch of tetras (maybe even 2 schools of 10), and a group of 6-8 corys. Lots of movement and colorful fish!
A 30 long is even a great size for a tiny tanganyikan community with shellis, cylindricus, and brichardi. (this is my next plan for a 30 long, anyway)