The male guppies would only come to 5inch total, since they are much smaller than females. The catfish (cory's?) can range from 1" to 4"... I am unfamiliar with them as we use plecos here. If you got the miniature ones, I don't see there being a problem!
If you look on this page, 1/4 of the way down you will see sizes and types :)
I like cory's after looking at these! I may just pick some up sometime.