Well I can tell you the Venestus will get too large for the tank. Their max length is 12 inches. I made the same mistake.... i bought one because they looked awesome and I had to give her up when she reached 8" because my 55 was just too small. Its hard to find homes for the big fishes, so I would get him a new home before he gets too large... you know? The other guys sound perfect. The electric yellows are a rewarding, colorful fish to keep. And a good starter cichlid. I dont know much about convicts other than they are really cool looking and prolific breeders. (if you have a male & female, expect fry.)
When it comes to cichlids you need to remember 2 things.
1:
keep a 1:2 ratio!!! 1 male to every 2 females. (minimum) This will ensure that the males you keep stay as BEAUTIFUL as possible, and will elliminate inter-breeding. (though not completely, it will deter the event). It will also minimize aggression shown towards the females (boys trying to mate) and aggression between the males (less competition if there are more ladies).
2: If you choose to handle aggression with over stocking or over feeding, over filtration is a MUST. Weekly waterchanges and a good filter.
Also, I forgot to mention, I have those little hitch-hiking snails in my tank... tons of the little guys and the cichlids have never ever been interested in them. They thrive without issue.
Good luck- they are a great fish to keep!