What kind of cichlid can I add to my tank?

[phoenixsuns]

Ok recently I had to give away my 2 tinfoil barbs, they got huge and outgrew my tank unfortunatly. Id like to replace them with one cichlid. Here is what I already have.

46g tank

1 large Yellow lab
1 large red tailed shark
2 bala sharks
2 angels
1 common pleco and 1 chinese algie eater

Im most worried about the angels. The RTS is the only fish I have thats killed anything the bala's keep to themselves as do the angels and the yellow lab is a bit agressive but dosent take it far as the rts. For the most part though they all get along pretty well, Id love to add 1 more cichlid but again Im a little worried he might a meal out of the slower swimming angel fish. Suggestions?
Here are some pics of my fish and my tank:

yellow lab
http/img.photobucket.com/albums/v453/pho...00/DSC00174.jpg

angels
http/img.photobucket.com/albums/v453/pho...00/DSC00186.jpg

Red tail shark
http/img.photobucket.com/albums/v453/pho...00/DSC00168.jpg

bala
http/img.photobucket.com/albums/v453/pho...00/DSC00195.jpg

the tank from afar, if you look in the upper left corner you'ss see the RTS latest victem (Albino rainbow shark)in the isolation tank, once I get him better he'll have to go, the rts will kill him if I put him back in.
http/img.photobucket.com/albums/v453/pho...00/DSC00153.jpg

 

[freddyk]

You can do more labs, they're social grouping fish anyway, but you're better off looking at new world cichlids in a tank like that.

 

[phoenixsuns]

So you think the angels would get pretty beat up than right?