I believe I bought my phantom at uavproducts.com. I haven't had problems, tho, so don't know what their customer service is like. I've heard it's very good (they shipped my phantom same day). Readymaderc.com is where I've gotten everything else and they're very responsive also.
But the phantom is one of the most impressive things I've ever bought packaging/completeness wise. They even have dabs of blue loctite on the supplied screws and a wrench for the prop nuts... you literally only need a screwdriver to put it together and go fly.
The other option is to do a build from a kit, then you get the DIY discount and a good machine for a decent price. That's what I did with my f550. Got the f550 ARF and the Naza V2; I don't recall I had to add anything else to get the kit itself up and running except my FPV stuff.
But yes for AP, it gets a lot more complicated because you have the camera mounts and landing gear, etc...
I'm partial to DJI myself, mainly because their kits are very complete and work well so far. Others, you have to do a little of this and a little of that and what on earth is this and what the heck do you use for that and where do I get that and.... That sort of thing. the stuff that can drive you crazy when moving to a new platform like I was and still am.
The high end DJI stuff tho is really pricey, so I have no idea how it compares...