Here's what I'd recommend.
Put together an offer sheet listing everything about the vehicle (color, options, ED invoice prices, etc.) and send it to the internet service managers via all of the dealerships e-mail address for the States you will consider buying from. Include the over invoice price you are seeking, then sit back and watch the replies come pouring back from these dealerships.
Once you've agreed to a price with one or more of them shop it to your local dealer of choice, and see if they will match or come close to it.
This is the method that I used when I was soliciting prices for my cab, and I was surprised at some of the replies that I got. My local dealer wouldn't match or even come close to the best offer, so I bought from the next nearest dealer that would. Take into consideration that by buying from a non-local dealer you may be giving up some perks like free loaners, Saturday car washes, etc.. Consider what those perks are worth to you, and use it to gauge the best non-local offer vs. the best local offer.
Personally I think 1.5K over is more realistic, but you never really know until you try. It is just an offer and provides the basis for further discourse once they've accepted or countered with their own offer.
You're making a great decision by going ED. In my opinion it's just about the only way to fly when buying BMW's. Not only do you save a hunk of dough, but you also get to drive it on the roads that it was really engineered for. And even after all of the travel expenses are added up, if you just break even on the deal the experience alone will stay with you for a lifetime. :thumbup: :thumbup:
Good luck and keep us posted on your efforts.