I don't think it really makes much difference who you go and buy your new apple from. By and large, you'll be charged the same price wherever you go, as resellers base themselves on apple's r.r.p. On the one hand, if you purchase directly from apple, then they get more of a profit from that item (direct sales are worth more to a company individually than sales to retailers, where they have to offer 10/20...% discounts). On the other hand, buying your new computer from a reseller provides support for the growing number of places selling macs, making it just that bit more likely that we'll see macs available in more and more places.
also consider non apple promotions. many resellers offer to throw in a printer, digital camera, ram, or software for "free" when you purchase a mac from them. i think printers and ram are pretty standard offers from resellers, the others happen only ocassionally. shipping costs and times should also weigh in on your decision.
some points that may not be valid with you. remember education discounts if you are associated with education on any level (or know someone who could purchase for you who is). also employee discounts are often substancial (got a friend at apple? ask them about it).
its hard to tell someone where the "best" place to buy is since it is a highly individual process, but if you keep in mind britboys comments and a few of mine you might find yourself a good price.