seems O.K. to me but I do have a couple possible points.
if the rams and angels are going to be mated pairs, I would use some caution, they can both make life somewhat miserable when spawning, maybe keep only the pair of rams for spawning? other than that, I beleive all fish share a common water type, neutral-lightly acidic. I'd add the rams after the tank had been set up for a long time because they are very sensitive to water parameters.
the clown loaches I'm not so sure about. I think a pack of corydoras would be more appropriate, or maybe some other loaches, but clowns eventually grow large and like to be in groups of 5 or more.
I know sevrums aren't that agressive, but I have no experience with them. maybe someone else will chime in about them.