I would shelf teh passer idea until your tank is just about fully stocked.....
You "may" be lucky and get a moderately aggressive one, but you will probably get a typically aggressive one, which will make it diffiult to introduce any medium to large bodied fish such as tangs, butterflies, angels, triggers, etc.
Maybe put together a "maybe" list and shoot it over to us..... we can have a look and give our thoughts.... that will give you a "feel" for te directino you want to go, and a "feel" for when you want to introduce th passer.... if at all......
Personally, while they are one of my favourinte fish (in my top 5) I have never had one because they are just too damn aggressive, get too big too quickly, and make life misery for all other tank mates..... nice fish, but for me, not worth the trade off.
HTH
Matt