The gold clown knife will get big. But there are lots of people keeping them in similar sized tanks so I won't tell you no. Plus I think you got time til over 2ft. Bear in mind it's max size though and have a plan of either eating it or a friend that will take it if it gets too big.
As far as cats. Jaguar cats are cool and small, lima shovelnose would work, possibly even a tigrinuis cat(not TSN but Tigrinus) for a while. Gulper is another cool cat but not if you have anything the same size of it or smaller as it will eat it.