I'm a bit confused by the post, but think that you are looking for a pair of New Worlds for a 75 that are relatively peaceful. If that's the case, here are a few suggestions. If not, sorry.
- Archocentrus Centrarchus - Really one of my favorite fish. Pretty peaceful, get a beautiful green, gold, and black coloration as adults. They will turn almost completely pitch black when spawning. Males max out at 7" +/-, females a bit smaller.
- H. Nicaraguensis - Another mid sized growing fish with golds and blues. Females are usually the more colorful of the pair. Males get to 8-9", females a couple inches smaller. They can be a bit pushy, but not evil IME.
- Many of the Aequidens species would also fit the bill. Metae, diadema, and patricki are all beautiful.