If you are reffering to your current 10 gallon, don't add anything at all to it - cichlid or otherwise - it's already over-stocked and neither the cories nor danios are ideal for that size tank (the cardinals aren't realy either but will be ok).
If it's an empty 10 gallon, shell-dwellers (neolamprologus multifasciatus in particular) are a good choice but they are african - not new world - and they ahve some very specific requirements so you need to research them very thoroughly before even considering them.
