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.
Everything sounds great in my opinion except for the severum. They grow quite large especially in comparison to some of your other fish listed. I may also, like rjl420 says try something other then the clown loaches. They get a bit on the large size, and enjoy big groups.
Add good filtration if you think your tank is overstocked. As a backup, I use a fluidized bed filter. And you can use a emperor 400. That way, its EASY to clean the pads every other day if needed. A canistor can take longer to clean and may cause you to clean it less. an emporor 400, you can remove the debris every other day if you choose..