I'm not sure why someone posted that the tetras would get eaten... I have a pair of rams with a small group of cardinals (for about 6 months so far), and there has never been any problems. Maybe other cichlids are prone to eating smaller fish, but my rams are quite gentle until breeding time, and then they only run the fish away from the eggs.
As for the kuhlis, if you get the plain black ones they are more active. I have some that are out all the time, hanging out in the plants, scavenging for food, whatever.
I'd go with a pair of rams, either 3 cories or 3-5 black kuhlis, and a small group (maybe 6) of the smaller tetras (cardinals, rummynose, etc). You may even want to consider hatchetfish instead of the tetras. They hang out at the top, so the middle would be wide open for your rams, and the bottom would be covered with the cories/kuhlis.
HTH!