Sounds about what I was thinking. Already figured the red devils were going to be "You'll be lucky to be rid of them" types that nobody wants just from their size (they're twice as big as anything else in the tank) and infamous behavior alone.I can't speak to the loaches. Not much of a loach guy. I can give you some guidance on the cichlids, however.
You don't have anything too exotic, so don't expect too much. The red devils and parrots are a dime a dozen and also mean, nasty tempered fish. Red devils are tank busters to boot. I'd advertise at $10.00 or best offer each. Take $5.00 without even haggling. Regardless, your best bet is to take what is offered and get rid of them to the first person that shows any interest, even if you have to give them away. Don't get too stubborn with your haggling.
Green terrors are a bit better and if they're on the larger side you may get $10.00 each. Do you know the sexes? A male and female might get you $30.00 even if they aren't a proven breeding pair. Sexing would also be helpful, because a hobbyist may be looking for one sex or the other to pair up with a fish they already have. If you know the sexes I'd advertise $15.00 each. If you have pics I could probably help with that. Otherwise, I'd advertise $10.00 each and settle for $5.00. I'm assuming that these are just regular garden-variety green terrors and not one of the other Andinoacara species.
The severum is an interesting case. There are so many related species from the genus Heros in the hobby that use "severum" in the name. If you do happen to know which species of "severum" you may be able to ask $25.00 to $30.00. If you don't know specifically which Heros species you have, expect $5.00 to $15.00, with $5.00 if it's on the smaller size and maybe $15.00 if it's on the larger size of the range you mentioned.
The acei are probably worth a solid $5.00 if they're on the 4" side. I'd advertise for $10.00 if they were closer to 6".
Like is said, I'd definitely take the first offer that came my way on the parrots and red devils. The rest really depend on how quickly you want to get rid of them. If you hold out you could probably find some one that will pay your asking price, but it might take some time to find that person.
Hope this helps. Good luck!
I think the green terrors might be both females. Same size with no particular difference in appearance except the rims of their tails (one's is orange the other's is white).
No clue about the severum. It's a wild type color from what I can tell, muddied greenish brown with vertical black lines along the body and faded red anal fin.
One of the acei is a baby and I have no idea how it's still alive among the giant red devils.
The really unfortunate thing is that it'd be extremely difficult to find someone who'd take the whole lot considering what an incompatible mess the community is (the previous owner was an elderly gentlemen who undoubtedly didn't do much if any research and just threw a bunch of cichlids together). Regardless I'll give it a shot and if I can sell at least some of them it'd be great.