What I would do is spend considerable time on You Tube watching vids from the different large quads. Have watched one who was using pro level equipment flying in Washington state, I think, that is incredible, very smooth, very beautiful. Was one that really grab my attention for what could be. Very expensive stuff, belt drive gimbals, which is a must for very smooth work. With your budget, I would look for a unit that will do a still as well as a video camera lift.
So my list of must have would look something like this:
Carbon fiber.
More motors the better, octagon.
Best quality motors I can find-Tiger pancake.
WooKong.
Belt drive, carbon fiber Gimbal-3 axes.
Able to carry the camera plus FPV gear.
FPV gear for knowing what the camera is actual seeing.
Doubt your budget is enough for all the above. You have the Naza. Seems some debate between the Naza and the Wookong for camera work. So start with what you have and spend the budget on the frame, motors and gimbal.
Good Tiger motors, which get very high ratings, are just under $80 X 8 + $640 as an example of how fast it will add up. Would use the Tiger ESC to go with there motors, under $20 X 8 + $160. Adds up very quick. Might be a bargin to purchase one of the pro level already built.
Have fun shopping and doing your research. Would love to do such a build. Will be satisfied with my QAV500, which does very good camera work with the Go Pro 2. Bye the way, the book keeper says, with all the mistakes I made, have very close to your bottom line budget invested. Adds up very quick. Double your budget.
Oh yes! In the mean time fly, fly, fly, fly. Did I say fly what you have until you are very very very good.