May I have your suggestions please?

A while back I got some great suggestions here and I'm looking for more. We have a 29 gal. planted tank and are looking for 1 - 3 "main" fish to complete the stocking. We were thinking some type of dwarf or small peaceful cichlid (low pH). The tank has 4 cardinal tetras, 4 small killies, 2 pristella tetras, 1 cory cat, and 1 bolivian ram. The plan was to have a pair or a few of the rams but we have not had sucess. We always end up with one. I'm not sure if it is aggression or health issues but we are ready to try something else. We also had a successful pair of kribensis in here which were nice but the aggression at breeding time was no fun to watch so we gave them away. So...... what can you suggest that gets 3-4", is interesting, "good looking", hardy, peaceful, fits with the current fish? Thanks in advance!