55 gallon stocking questions?

I just bought a 55 gallon tank (by "just" I mean about 2 monthes ago) and have been cycling it for a month, it has a aquaclear 40-70 gallon or something like that (300 gallons per hour). Right now there are 1 female molly, 1 female platty, 1 royal pleco, and 6 neon tetra's. The platty, molly, and tetras can be moved to another tank if needed. Heres my question: What should I put in the tank? I was thinking maybe an african cichlid tank. I would like it to be colorful and active. I would like at least 1 fish around 5" long (more or less) as a center piece. Any recommendations? I am willing to put lots of time and effort on this. My budget is prettly low, I'd rather not spend a whole lot on extra things.