Advice on partial restocking

I run a medium-high light planted 40 gallon tank, and I need to get a new focal fish or two. My current pair of Opaline Gouramis is not working out and will be going back to the LFS. All I want is a pair of fish that are 3-6 inches, not too agressive, and interesting or well colored. The Gouramis were getting too agressive with each other and the other fish. I have read that Pearl Gouramis are less agressive, but i have doubts due to my opalines, and because they seem more difficult to sex. Ram Cichlids, or any other mostly peaceful species sounds good, but I have concerns about them around plants and shrimp. Any advice on these or suggestions of other fish would be greatly appreciated.

40 Gallon tank residents:
2 Opaline Gourami (Leaving soon)
4 Panda Corydorus
4 Otocinclus
1 Hillstream Loach
10 Harlequin Rasbora
3 Amano Shrimp
1 ADF

Thank you, I am leaning towards the Rams myself. Now to decide on what kind really. I went to my best LFS and asked if they could get German Rams, and they said no, but they could get Blue, Gold, Clown and Wild Rams. I thought Blue and German were the same thing, and I have never heard of Clown or Gold. I think I need to poke around the Cichlid forum for some dirt on these guys. Any information people feel like volunteering is also good.