Hi...I had a Naso for close to 6 years..started as a 1 1/2" juv..quickly grew to 8". He was definitely cramped in a 6ft long 225G...actually died from a puncture wound swiming into a vert.snail (had a major 'breakout'). This fish needs a lot of room...too bad, because they are mild mannered, hardy feeders...just grow big and aren't to happy when they can't cruise.
My emp started as a 2"-3" juv and and the best part was watching the transition of colors from juvie to Adult...one of the more gratifying aspects of keeping this fish. Got him in '97...I'll try to attach a pic from 4yrs ago, so I would have had him for around 5 years at the time of this pic and he had almost full colors, except a few lines along his top that still were going to straighten out...and his 'mask' on his face wasn't quite done yet.... don't have any recent pics....but he's a full adult now...about 11".
Good diet, (selcon and vitachem on everything)...stable tank and stability of the fish's environment (ie. stop adding stuff) and your Angel will get it's full colors, no problem.
The other fish you are considering: Tusk grows large once/if it gets to feeding properly.....the D.Tang: I'd have to look up...no idea/no experience with it.
Potters can be one of the tougher pygmys to get to eat, hit or miss with them...clowns need a home to be happy (My mated percs live in an empty conch shell...didn't want to try and keep anemones), but are easy to feed/keep...the hawk I know nothing about.
I'll try and add the pic here: btw: kudos to you for making a plan ahead of time, researching the fish, and getting folks opinions on the plan. A majority of the problems folks are having with their tanks that you read about on these boards could be avoided with any fish/livestock if they had done what your doing before buying something....make a plan, stick to it, take your time (nothing happens fast in this hobby)...and then leave it alone and enjoy. good luck!