Just for the record, DG will not match the discount on the apple (CX) website.
It is worth knowing what you can do through apple direct before you go to negotiate. Items like memory (non apple stuff) is the area they can compete on and bring the price down on but for a lot of stuff it is cheaper through the apple site.
I checked a number of places today for the purchase of a mac with warranty and extra memory and hard drive options.
Cheers