Ideas for a cichlid tank

Hello. I don't normally post here, but I do read it.

Anyway - I have a 4ft tank which I want to slowly convert to be
a cichlid tank. At present it contains 2 nocturnal catfish
(a pleco and similar, which hide by day under wood), 4 kribs,
3 clown loaches and 3 tiger barbs.

Some of the older smaller fish have died off or been moved
recently leaving me with those. I don't expect the tiger barbs
to live much longer (they look fullgrown and battleworn) but
they keep surprising me. So that leaves the loaches, which will
soon be too big to move elsewhere, and the catfish and kribs.

I'd like to add more cichlids and gradually turn it into a
cichlid tank, but obviously along the way, the fish have to get
along. I don't know much about cichlids except that a) they
can be aggressive and b) gouramis are supposed to be easyish.

My water parameters are medium-hard (12KH ish) and 7.8pH.

I'd love some suggestions for what sort of fish to try, and
which I could introduce now, which I'd need to wait until the
tigers are gone, etc. The tigers don't seem to pick on any other
fish (as I said, they are quite old!) although the kribs get
territorial when laying eggs (not that they ever hatch).

A little more info: the tank is 48x15x15 inches, it's planted
quite heavily along the back and also has some bogwood, slate
etc - only the front half of the tank is bare, which means there
is lots of swimming space as well as room to hide; there's a
reasonable current as I have an external filter output at one
end and a supplementary internal filter at the other; the
clowns are about 2.5", 3" and 5", and I think the catfish are
about 7" but I never see them by day! The kribs are a mature
pair, and a pair of juveniles which are about 2/3 grown.

All advice/interesting solutions welcome.

--
Flash Wilson