It depends on what is actually in the tank. Lots of people try to get rid of problem fish, and end up giving away their tank.....thinking the problem goes away.....It DOESN'T go away.
Find out what kind of "catfish" you have....IF it is a common pleco, it can't be kept in a tank that size....so it has to go...often you can take them to your
LFS and give it away....or if you know someone with oscars that need one...ALSO
CAE's are not a good community tank fish.
As for the others, you should be able to work them together with what you already have. I wouldn't plan on new fish at this point, that tank isn't actually very big.