The best "place" to pre-order was up until about 2 weeks ago when they were doing the 50%+ off sales everywhere.
I don't know that there's any advantage to pre-ordering at full retail right now, Amazon or elsewhere. If Amazon gets delayed, for example, you might very well want to go to your local computer store upon release and grab it off the shelf instead. It's not like the price is going to go up any further.
Given they're supposed to have those family 3-packs coming out, and given they may even do some other sale again closer to release, I'd personally hold off on pre-ordering at this stage.