Well, in a 500 gallon tank, I don't $3,000 will go very far in regards to livestock. Think about it. That is really only about 60 pieces of coral - not even counting fish. That is not that much coral in a tank that size. Of course, your stocking should be done over a long period of time. It's not like you are going to go blow $3,000 as soon as you get the tank set up. Please, whatever you do, don't do that.
The other thing to consider is there are no guarantees that your tank won't crash and you will lose everything in it. It has happened to me and to DaveK and a whole lot of other people out there - even Eric Borneman and
Steve Weast. A huge tank means potential huge financial losses if it goes south. Definitely something to consider if money is a concern.
Honestly, if it were me, I would go with a tank of about 200 gallons in size. You could still get Aquarium Obsessed or Miracles to build the tank and get Starphire glass - which I would highly recommend on a tank this size. The thing is, a tank of this size will do everything you want to accomplish and still not be insanely expensive to put together. It won't be cheap, but compared to something two or three times larger, a lot more reasonable. Maybe get a price on a 200 or 225.