I am not sure weather it is possible or not, but many cichlids are capable of cross breeding between species. While it may seem interesting, caution should be used. Under no circumstances should the offspring be sold, traded, given away to friends or in any other way circulated in the trade. Just do a search on cross breeding and you will get numerous hits on the subject here on AC. Some cichlids are next to impossible to get as pure strains due to unreported cross breeding. If you do plan on breeding, i would suguest taking a mated pair from the 55 and setting up a smaller tank with only those 2 fish for that purpose.
In my 55 I have a pair of Appistogramma cacatoides and a pair of rams(sold as A. ramizri, as the LFS has a very old book used for ID that was published prior to the reclassifiacation of microgeophagus. The reason I added that is I initially thought I had 2 pairs of Apistos) and it seems to me there is more than enough room for both to have thier own niche in the aquarium.