dwarf cichlids

I would suggest, if you've a mind to try Apistos then Cacatuoides would probably be one of the 'safest' starters.
Bolivian Rams, another nice-looking yet pretty hardy Dwarf, the ever popular Krib, Aequidens Curviceps, although the genus has been reclassified now to something beginning with an 'L'.
Others worth trying as a 'starter' dwarf might be Nannacara Anomola and the African Butterfly dwarf Cichlid (the latin name of which escapes me for the moment but someone will know it) (they were known as Pelmatachromis Thomasi in the old days, but they, again, have been reclassified into a new genus now).
Those are a few worthy of checking out, but doubtless others here will have others to suggest.
John

One thing I omitted to add to last night's answer.
At heart Dwarf Cichlids are just little Cichlids (obvious, really) but they still have the same territorial instinct and can be equally - if not more so - aggressive as their larger cousins.
It might be that in such a small tank as you plan to use this trait may just become even more evident than in a somewhat larger one.
Plenty of hiding spaces - including a 'sort of' barrier between each half of the tank may help. Sometimes this isn't always necessary as may just you get a pair which seem 'happy' with each other's company but...it's as well to be aware of the potential 'danger' which might be ahead.
Some times you can get away with adding a few of what those in the know call 'dither fish' - smaller more innocuous fish upon which the Dwarf Cichlids can take out their aggression - sometimes combining to constantly attack (if they could catch them!) what they must come to see as 'intruders'.
Classic examples, I find, are things like Cherry and Chequer Barbs, some Characins, livebearers (especially Guppies) - the list goes on and everybody has their own personal favourites.

John

Sorry, I miised this earlier.
I also misread your tank size, for some inexplicable reason I read 16ltr instead of 16 gallons.
Hopefully it's something like 30x12x12?
This would be marginally preferable to a less-wide, deeper tank.
Anyway, it seems you've settled on Rams which might be a good choice if you can get some European-bred ones. I'm no fan of those from the Far East (as I have 'hinted' previously).
It really is a bit of a hard call - I personally would go for three, or even four but would get them together and introduce them into the tank together as well.
Others may differ and I'm only telling you what I personally would do.
My inclination would be - if at all possible - to get 1 male and three females, the latter seeming to be a bit more tolerant of one another (but only a bit).
If you can manage it some small Corys would be good tank-mates and, as previously suggested, some 'dither' fish (I hate that description, without any valid reason).
Introduce them all with the lights turned off for a few hours and watch how things progress. There will be a good bit of 'shaping up' done, along with some mock battles but hopefully things will settle down over time and each will claim its own part of the tank as its personal territory.
Now, all this may just be a bit 'over the top' and they all settle down with each other peacefully - I've had it happen both ways with Rams so it's as well to be prepared for the worst case scenario.
When will you be getting your new fish? - Presumably you have to find a new home for the Convicts first?
Let us know how things work out, we all seem pretty interested in Dwarf Cichlids (at least quite a lot are).
John