#1 thing....patience !!!
Once you get water in the tank, you have a couple of weeks (maybe more) to sit and look at the water !!!
I would advise you to READ alot about clowns and tangs and get to know their individual needs.
Putting 2 pairs of clowns together could prove interesting, especially if they were maroons !!! And then there is the anemone point....WAIT !!! You can buy 2 now, and probably kill them, or let the tank mature and possibly keep them alive. The best thing though is to SLOW DOWN !!! The Chevron is an expensive fish to hurt. Slow down and read. Let the water do its magic. You might find something you want to put in instead of one of the fish you listed. I think your choices are wise, but you are going to need massive filtration to accomodate all those inches of fish !!!