Here is what I know.
Years ago, I had a 20 gal, with gravel, some cement block pieces, and some live plants (easy weedlike stuff, that doesn't require expensive lighting)
I put in about 6 Ciclids, from 1 1/2 - 2 inches, and my plan was to possibly remove some, if once they matured it seemed overstocked. It was a varitey of breeds, but I had 2 Brichardi, because it was my favorite when i purchased them, and I had heard they may breed.
I don't remember exactly, but within a few weeks my friend said "Hey Look!" and right there in the center of this community tank, the small (barely 2 inch) couple, had formed a bed in the gravel, and there was a tiny cloud of babys. Then honestly i dont remember what happened. I moved shortly after, and i think i gave all the fish to friends or petstore, and until this new tank i set up recently, have not had anything.
The point of the story is though, Poeple who say you "NEED" some particular substrate, or spawning place, or that you "CAN'T" put a breeding couple with anything else, are... well.... wrong. They just are relating personal experience with what worked for them, or how their fish had a bad temper.
Personaly I like more natural stuff than bright colored fake stuff, but what you have is not going to prevent fish from breeding. But my advice is go to a landscape yard, buy a huge bag of gravel for a few cents a pound, and you just have to rinse the dirt off it. WAYY cheaper than expensive little one pound bags from petstore. Also I bought some flag stone also pretty cheap, to stack and make cool structures.
From what i know, there is no real way to sex young brichardis, except to either buy a mated pair, or buy a bunch of young, and wait and see.
I belive that what was said about "Only a pair to a tank, period" was not neccisarily true, maybe a large pair in a small tank, but a small pair in a 20 gal wide tank like you have, and there is no reason I dont think you could add a few other Ciclids of the same size. Add hiding places accross the tank, and they will find their own turf.