Hey computerman! Welcome to AC!
While Angels and Gouramis can sometimes get along, they also might fight, as you have seen with your fish. If the behavior continues, you may have to return one of them, especially if there is a size difference between them. It is unlikely that it will work out.
Can you tell us more about your tank? Having as much information as possible allows us to answer questions more easily and accurately.
What size is it?
Do you have a filter and a heater?
Do you have water-testing kits?
Do you do water changes on the tank? How much and how often?
As far as your other fish -
Guppies do better in groups with one male and two or more females. Since male guppies spend almost all of their time chasing females and trying to mate, having several females allows each one some time to relax and not be bothered by the male. If there is only one female, it is easy for her to get stressed by the constant chasing, and possibly get sick and die from never having time to rest or escape.
Could you find out what kind of catfish you have? Petsmart sells a wide variety of catfish, from little Cory cats that only reach 3 inches, to common plecos that can reach 18-24 inches, or Afrcian syno cats, or even Asian catfish which can grow huge! Some of them like to be in groups, like the cories, while others can be fine on their own. A lot of them are only good for larger tanks, though.
Speaking of catfish in groups, the Glass Catfish is one of those. While some people have good luck keeping them individually, most people will say that they really need to be in larger groups. Apparently they act, swim, eat, and overall simply live better when they have others of their own kind.